An abortion is the termination of a pregnancy by the removal or expulsion of an embryo or fetus from the uterus, resulting in or caused by its death. An abortion can occur spontaneously due to complications during pregnancy or can be induced. Abortion as a term most commonly refers to the induced abortion of a human pregnancy, while spontaneous abortions are usually termed miscarriages.
Abortion has a long history and has been induced by various methods including herbal abortifacients, the use of sharpened tools, physical trauma and other traditional methods. Modern medicine utilizes medications and surgical procedures to induce abortion. The legality, prevalence, and cultural views on abortion vary substantially around the world. In many parts of the world there is a divisive public debate over the ethical and legal aspects of abortion between the pro-life and pro-choice movements. The approximate number of induced abortions performed worldwide in 2003 was 42 million, which declined from nearly 46 million in 1995.
See main article: Miscarriage.
Spontaneous abortion (also known as miscarriage) is the expulsion of an embryo or fetus due to accidental trauma or natural causes before the 20th week of gestation. Most miscarriages are due to incorrect replication of chromosomes; they can also be caused by environmental factors. A pregnancy that ends between 20 and 37 weeks of gestation, if it results in a live-born infant, is known as a "premature birth". When a fetus dies in utero after about 20 weeks, or during delivery, it is usually termed "stillborn". Premature births and stillbirths are generally not considered to be miscarriages although usage of these terms can sometimes overlap.
Between 10% and 50% of pregnancies end in clinically apparent miscarriage, depending upon the age and health of the pregnant woman. Most miscarriages occur very early in pregnancy, in most cases, they occur so early in the pregnancy that the woman is not even aware that she was pregnant. One study testing hormones for ovulation and pregnancy found that 61.9% of conceptuses were lost prior to 12 weeks, and 91.7% of these losses occurred subclinically, without the knowledge of the once pregnant woman. Some pregnancy losses are "ignored as conceptions," one study of 232 pregnant women showed “virtually complete [pregancy loss] by the end of the embryonic period" with a pregnancy loss rate of only 2 precent after 8.5 weeks after the last menstrual period.
The risk of spontaneous abortion decreases sharply after the 10th week from the last menstrual period (LMP).  The most common cause of spontaneous abortion during the first trimester is chromosomal abnormalities of the embryo/fetus, accounting for at least 50% of sampled early pregnancy losses. Other causes include vascular disease (such as lupus), diabetes, other hormonal problems, infection, and abnormalities of the uterus. Advancing maternal age and a patient history of previous spontaneous abortions are the two leading factors associated with a greater risk of spontaneous abortion. A spontaneous abortion can also be caused by accidental trauma; intentional trauma or stress to cause miscarriage is considered induced abortion or feticide.
A pregnancy can be intentionally aborted in many ways. The manner selected depends chiefly upon the gestational age of the embryo or fetus, which increases in size as it ages. Specific procedures may also be selected due to legality, regional availability, and doctor-patient preference. Reasons for procuring induced abortions are typically characterized as either therapeutic or elective. An abortion is medically referred to as therapeutic when it is performed to:
See main article: Medical abortion.
"Medical abortions" are non-surgical abortions that use pharmaceutical drugs, and are only effective in the first trimester of pregnancy. Medical abortions comprise 10% of all abortions in the United States and Europe. Combined regimens include methotrexate or mifepristone, followed by a prostaglandin (either misoprostol or gemeprost: misoprostol is used in the U.S.; gemeprost is used in the UK and Sweden.) When used within 49 days gestation, approximately 92% of women undergoing medical abortion with a combined regimen completed it without surgical intervention. Misoprostol can be used alone, but has a lower efficacy rate than combined regimens. In cases of failure of medical abortion, vacuum or manual aspiration is used to complete the abortion surgically.
In the first 12 weeks, suction-aspiration or vacuum abortion is the most common method. Manual Vacuum aspiration (MVA) abortion consists of removing the fetus or embryo, placenta and membranes by suction using a manual syringe, while electric vacuum aspiration (EVA) abortion uses an electric pump. These techniques are comparable, and differ in the mechanism used to apply suction, how early in pregnancy they can be used, and whether cervical dilation is necessary. MVA, also known as "mini-suction" and "menstrual extraction", can be used in very early pregnancy, and does not require cervical dilation. Surgical techniques are sometimes referred to as 'Suction (or surgical) Termination Of Pregnancy' (STOP). From the 15th week until approximately the 26th, dilation and evacuation (D&E) is used. D&E consists of opening the cervix of the uterus and emptying it using surgical instruments and suction.
Dilation and curettage (D&C), the second most common method of abortion, is a standard gynecological procedure performed for a variety of reasons, including examination of the uterine lining for possible malignancy, investigation of abnormal bleeding, and abortion. Curettage refers to cleaning the walls of the uterus with a curette. The World Health Organization recommends this procedure, also called sharp curettage, only when MVA is unavailable. The term D and C, or sometimes suction curette, is used as a euphemism for the first trimester abortion procedure, whichever the method used.
Other techniques must be used to induce abortion in the second trimester. Premature delivery can be induced with prostaglandin; this can be coupled with injecting the amniotic fluid with caustic solutions containing saline or urea. After the 16th week of gestation, abortions can be induced by intact dilation and extraction (IDX) (also called intrauterine cranial decompression), which requires surgical decompression of the fetus' head before evacuation. IDX is sometimes called "partial-birth abortion," which has been federally banned in the United States. A hysterotomy abortion is a procedure similar to a caesarean section, and is performed under general anesthesia because it is considered major abdominal surgery. It requires a smaller incision than a caesarean section and is used during later stages of pregnancy.
From the 20th to 23rd week of gestation, an injection to stop the fetal heart can be used as the first phase of the surgical abortion procedure     to ensure that the fetus is not born alive.
Historically, a number of herbs reputed to possess abortifacient properties have been used in folk medicine: tansy, pennyroyal, black cohosh, and the now-extinct silphium (see history of abortion). The use of herbs in such a manner can cause serious — even lethal — side effects, such as multiple organ failure, and is not recommended by physicians.
Abortion is sometimes attempted by causing trauma to the abdomen. The degree of force, if severe, can cause serious internal injuries without necessarily succeeding in inducing miscarriage. Both accidental and deliberate abortions of this kind can be subject to criminal liability in many countries. In Southeast Asia, there is an ancient tradition of attempting abortion through forceful abdominal massage. One of the bas reliefs decorating the temple of Angkor Wat in Cambodia depicts a demon performing such an abortion upon a woman who has been sent to the underworld.
Reported methods of unsafe, self-induced abortion include misuse of misoprostol, and insertion of non-surgical implements such as knitting needles and clothes hangers into the uterus. These methods are rarely seen in developed countries where surgical abortion is legal and available.
Early-term surgical abortion is a simple procedure which is safer than childbirth when performed before the 16th week.  Abortion methods, like most minimally invasive procedures, carry a small potential for serious complications.  The risk of complications can increase depending on how far pregnancy has progressed. 
Women typically experience minor pain during first-trimester abortion procedures. In a 1979 study of 2,299 patients, 97% reported experiencing some degree of pain. Patients rated the pain as being less than earache or toothache, but more than headache or backache. Local and general anesthetics are used during surgical procedures
See main article: Abortion and mental health. The relationship between induced abortion and mental health is an area of controversy. No scientific research has demonstrated a direct causal relationship between abortion and poor mental health, though some studies have noted that there may be a statistical correlation. Pre-existing factors in a woman's life, such as emotional attachment to the pregnancy, lack of social support, pre-existing psychiatric illness, and conservative views on abortion increase the likelihood of experiencing negative feelings after an abortion. 
In a 1990 review, the American Psychological Association (APA) found that "severe negative reactions [after abortion] are rare and are in line with those following other normal life stresses." The APA revised and updated its findings in August 2008 to account for the accumulation of new evidence, and again concluded that induced abortion did not lead to increased mental health problems.  As of August 2008, the United Kingdom Royal College of Psychiatrists is also performing a systematic review of the medical literature to update their position statement on the subject.
Some proposed negative psychological effects of abortion have been referred to by pro-life advocates as a separate condition called "post-abortion syndrome." However, the existence of "post-abortion syndrome" is not recognized by any medical or psychological organization, and some physicians and pro-choice advocates have argued that the effort to popularize the idea of a "post-abortion syndrome" is a tactic used by pro-life advocates for political purposes.   
The incidence and reasons for induced abortion vary regionally. It has been estimated that approximately 46 million abortions are performed worldwide every year. Of these, 26 million are said to occur in places where abortion is legal; the other 20 million happen where the procedure is illegal. Some countries, such as Belgium (11.2 per 100 known pregnancies) and the Netherlands (10.6 per 100), have a low rate of induced abortion, while others like Russia (62.6 per 100) and Vietnam (43.7 per 100) have a comparatively high rate. The world ratio is 26 induced abortions per 100 known pregnancies.
Abortion rates also vary depending on the stage of pregnancy and the method practiced. In 2003, from data collected in those areas of the United States that sufficiently reported gestational age, it was found that 88.2% of abortions were conducted at or prior to 12 weeks, 10.4% from 13 to 20 weeks, and 1.4% at or after 21 weeks. 90.9% of these were classified as having been done by "curettage" (suction-aspiration, Dilation and curettage, Dilation and evacuation), 7.7% by "medical" means (mifepristone), 0.4% by "intrauterine instillation" (saline or prostaglandin), and 1.0% by "other" (including hysterotomy and hysterectomy). The Guttmacher Institute estimated there were 2,200 intact dilation and extraction procedures in the U.S. during 2000; this accounts for 0.17% of the total number of abortions performed that year. Similarly, in England and Wales in 2006, 89% of terminations occurred at or under 12 weeks, 9% between 13 to 19 weeks, and 1.5% at or over 20 weeks. 64% of those reported were by vacuum aspiration, 6% by D&E, and 30% were medical. Later abortions are more common in China, India, and other developing countries than in developed countries.
A 1998 aggregated study, from 27 countries, on the reasons women seek to terminate their pregnancies concluded that common factors cited to have influenced the abortion decision were: desire to delay or end childbearing, concern over the interruption of work or education, issues of financial or relationship stability, and perceived immaturity. A 2004 study in which American women at clinics answered a questionnaire yielded similar results. In Finland and the United States, concern for the health risks posed by pregnancy in individual cases was not a factor commonly given; however, in Bangladesh, India, and Kenya health concerns were cited by women more frequently as reasons for having an abortion. 1% of women in the 2004 survey-based U.S. study became pregnant as a result of rape and 0.5% as a result of incest. Another American study in 2002 concluded that 54% of women who had an abortion were using a form of contraception at the time of becoming pregnant while 46% were not. Inconsistent use was reported by 49% of those using condoms and 76% of those using the combined oral contraceptive pill; 42% of those using condoms reported failure through slipping or breakage. The Guttmacher Institute estimated that "most abortions in the United States are obtained by minority women" because minority women "have much higher rates of unintended pregnancy."
Some abortions are undergone as the result of societal pressures. These might include the stigmatization of disabled persons, preference for children of a specific sex, disapproval of single motherhood, insufficient economic support for families, lack of access to or rejection of contraceptive methods, or efforts toward population control (such as China's one-child policy). These factors can sometimes result in compulsory abortion or sex-selective abortion.
See main article: History of abortion. Induced abortion can be traced to ancient times. There is evidence to suggest that, historically, pregnancies were terminated through a number of methods, including the administration of abortifacient herbs, the use of sharpened implements, the application of abdominal pressure, and other techniques.
The Hippocratic Oath, the chief statement of medical ethics for Hippocratic physicians in Ancient Greece, forbade doctors from helping to procure an abortion by pessary. Soranus, a second-century Greek physician, suggested in his work Gynaecology that women wishing to abort their pregnancies should engage in energetic exercise, energetic jumping, carrying heavy objects, and riding animals. He also prescribed a number of recipes for herbal baths, pessaries, and bloodletting, but advised against the use of sharp instruments to induce miscarriage due to the risk of organ perforation. It is also believed that, in addition to using it as a contraceptive, the ancient Greeks relied upon silphium as an abortifacient. Such folk remedies, however, varied in effectiveness and were not without risk. Tansy and pennyroyal, for example, are two poisonous herbs with serious side effects that have at times been used to terminate pregnancy.
During the medieval period, physicians in the Islamic world documented detailed and extensive lists of birth control practices, including the use of abortifacients, commenting on their effectiveness and prevalence. They listed many different birth control substances in their medical encyclopedias, such as Avicenna listing 20 in The Canon of Medicine (1025) and Muhammad ibn Zakariya ar-Razi listing 176 in his Hawi (10th century). This was unparalleled in European medicine until the 19th century.
Abortion in the 19th century continued, despite bans in both the United Kingdom and the United States, as the disguised, but nonetheless open, advertisement of services in the Victorian era suggests.
In the 20th century the Soviet Union (1919), Iceland (1935) and Sweden (1938) were among the first countries to legalize certain or all forms of abortion. In 1935 Nazi Germany, a law was passed permitting abortions for those deemed "hereditarily ill," while women considered of German stock were specifically prohibited from having abortions.   
See main article: Sex-selective abortion and female infanticide.
It is suggested that sex-selective abortion might be partially responsible for the noticeable disparities between the birth rates of male and female children in some places. The preference for male children is reported in many areas of Asia, and abortion used to limit female births has been reported in Mainland China, Taiwan, South Korea, and India.
In India, the economic role of men, the costs associated with dowries, and a Hindu tradition which dictates that funeral rites must be performed by a male relative have led to a cultural preference for sons. The widespread availability of diagnostic testing, during the 1970s and '80s, led to advertisements for services which read, "Invest 500 rupees [for a sex test] now, save 50,000 rupees [for a dowry] later." In 1991, the male-to-female sex ratio in India was skewed from its biological norm of 105 to 100, to an average of 108 to 100. Researchers have asserted that between 1985 and 2005 as many as 10 million female fetuses may have been selectively aborted. The Indian government passed an official ban of pre-natal sex screening in 1994 and moved to pass a complete ban of sex-selective abortion in 2002.
In the People's Republic of China, there is also a historic son preference. The implementation of the one-child policy in 1979, in response to population concerns, led to an increased disparity in the sex ratio as parents attempted to circumvent the law through sex-selective abortion or the abandonment of unwanted daughters. Sex-selective abortion might be an influence on the shift from the baseline male-to-female birth rate to an elevated national rate of 117:100 reported in 2002. The trend was more pronounced in rural regions: as high as 130:100 in Guangdong and 135:100 in Hainan. A ban upon the practice of sex-selective abortion was enacted in 2003.
See main article: Unsafe abortion. Women seeking to terminate their pregnancies sometimes resort to unsafe methods, particularly where and when access to legal abortion is being barred.
The World Health Organization (WHO) defines an unsafe abortion as being "a procedure...carried out by persons lacking the necessary skills or in an environment that does not conform to minimal medical standards, or both." Unsafe abortions are known colloquially as "back-alley" abortions. This can include a person without medical training, a professional health provider operating in sub-standard conditions, or the woman herself.
Unsafe abortion remains a public health concern today due to the higher incidence and severity of its associated complications, such as incomplete abortion, sepsis, hemorrhage, and damage to internal organs. WHO estimates that 19 million unsafe abortions occur around the world annually and that 68,000 of these result in the woman's death. Complications of unsafe abortion are said to account, globally, for approximately 13% of all maternal mortalities, with regional estimates including 12% in Asia, 25% in Latin America, and 13% in sub-Saharan Africa. A 2007 study published in the The Lancet found that, although the global rate of abortion declined from 45.6 million in 1995 to 41.6 million in 2003, unsafe procedures still accounted for 48% of all abortions performed in 2003. Health education, access to family planning, and improvements in health care during and after abortion have been proposed to address this phenomenon.
See main article: Abortion debate, Pro-choice and Pro-life. In the history of abortion, induced abortion has been the source of considerable debate, controversy, and activism. An individual's position on the complex ethical, moral, philosophical, biological, and legal issues is often related to his or her value system. Opinions of abortion may be best described as being a combination of beliefs on its morality, and beliefs on the responsibility, ethical scope, and proper extent of governmental authorities in public policy. Religious ethics also has an influence upon both personal opinion and the greater debate over abortion (see religion and abortion).
Abortion debates, especially pertaining to abortion laws, are often spearheaded by advocacy groups belonging to one of two camps. In the United States, most often those in favor of greater legal restrictions on, or even complete prohibition of abortion, describe themselves as pro-life while those against legal restrictions on abortion describe themselves as pro-choice. Generally, the pro-life position argues that a human fetus is a human being with the right to live making abortion tantamount to murder. The pro-choice position argues that a woman has certain reproductive rights, especially the choice whether or not to carry a pregnancy to term.
In both public and private debate, arguments presented in favor of or against abortion focus on either the moral permissibility of an induced abortion, or justification of laws permitting or restricting abortion.
Debate also focuses on whether the pregnant woman should have to notify and/or have the consent of others in distinct cases: a minor, her parents; a legally married or common-law wife, her husband; or a pregnant woman, the biological father. In a 2003 Gallup poll in the United States, 79% of male and 67% of female respondents were in favor of spousal notification; overall support was 72% with 26% opposed.
See main article: Societal attitudes towards abortion.
A number of opinion polls around the world have explored public opinion regarding the issue of abortion. Results have varied from poll to poll, country to country, and region to region, while varying with regard to different aspects of the issue.
A May 2005 survey examined attitudes toward abortion in 10 European countries, asking polltakers whether they agreed with the statement, "If a woman doesn't want children, she should be allowed to have an abortion". The highest level of approval was 81% (in the Czech Republic); the lowest was 47% (in Poland).
In North America, a December 2001 poll surveyed Canadian opinion on abortion, asking Canadians in what circumstances they believe abortion should be permitted; 32% responded that they believe abortion should be legal in all circumstances, 52% that it should be legal in certain circumstances, and 14% that it should be legal in no circumstances. A similar poll in January 2006 surveyed people in the United States about U.S. opinion on abortion; 33% said that abortion should be "permitted only in cases such as rape, incest or to save the woman's life", 27% said that abortion should be "permitted in all cases", 15% that it should be "permitted, but subject to greater restrictions than it is now", 17% said that it should "only be permitted to save the woman's life", and 5% said that it should "never" be permitted. A November 2005 poll in Mexico found that 73.4% think abortion should not be legalized while 11.2% think it should.
Of attitudes in South America, a December 2003 survey found that 30% of Argentines thought that abortion in Argentina should be allowed "regardless of situation", 47% that it should be allowed "under some circumstances", and 23% that it should not be allowed "regardless of situation". A March 2007 poll regarding the abortion law in Brazil found that 65% of Brazilians believe that it "should not be modified", 16% that it should be expanded "to allow abortion in other cases", 10% that abortion should be "decriminalized", and 5% were "not sure". A July 2005 poll in Colombia found that 65.6% said they thought that abortion should remain illegal, 26.9% that it should be made legal, and 7.5% that they were unsure.
See main article: Abortion-breast cancer hypothesis. The abortion-breast cancer hypothesis (supporters call it the abortion-breast cancer link) posits that induced abortion increases the risk of developing breast cancer; it has been a controversial subject but the current scientific consensus has concluded that there is no significant association between first-trimester abortion and breast cancer risk.   
In early pregnancy, levels of estrogen increase, leading to breast growth in preparation for lactation. The hypothesis proposes that if this process is interrupted by an abortion before full maturity in the third trimester then more relatively vulnerable immature cells could be left than there were prior to the pregnancy, resulting in a greater potential risk of breast cancer. The hypothesis mechanism was first proposed and explored in rat studies conducted in the 1980s.  
See main article: Fetal pain. Fetal pain, its existence, and its implications are part of a larger debate about abortion. Many researchers in the area of fetal development believe that a fetus is unlikely to feel pain until after the seventh month of pregnancy.  However, legislation has been proposed by pro-life advocates requiring abortion providers to tell a woman that the fetus may feel pain during an abortion procedure.
A review by researchers from the University of California, San Francisco in JAMA concluded that data from dozens of medical reports and studies indicate that fetuses are unlikely to feel pain until the third trimester of pregnancy.  There is an emerging consensus among developmental neurobiologists that the establishment of thalamocortical connections (at about 26 weeks) is a critical event with regard to fetal perception of pain. Because pain can involve sensory, emotional and cognitive factors, it may be "impossible to know" when painful experiences are perceived, even if it is known when thalamocortical connections are established.
See main article: Legalized abortion and crime effect.
The suggestion was brought to widespread attention by a 1999 academic paper, The Impact of Legalized Abortion on Crime, authored by the economists Steven D. Levitt and John Donohue. They attributed the drop in crime to a reduction in individuals said to have a higher statistical probability of committing crimes: unwanted children, especially those born to mothers who are African-American, impoverished, adolescent, uneducated, and single. The change coincided with what would have been the adolescence, or peak years of potential criminality, of those who had not been born as a result of Roe v. Wade and similar cases. Donohue and Levitt's study also noted that states which legalized abortion before the rest of the nation experienced the lowering crime rate pattern earlier, and those with higher abortion rates had more pronounced reductions.
Fellow economists Christopher Foote and Christopher Goetz criticized the methodology in the Donohue-Levitt study, noting a lack of accommodation for statewide yearly variations such as cocaine use, and recalculating based on incidence of crime per capita; they found no statistically significant results. Levitt and Donohue responded to this by presenting an adjusted data set which took into account these concerns and reported that the data maintained the statistical significance of their initial paper.
Such research has been criticized by some as being utilitarian, discriminatory as to race and socioeconomic class, and as promoting eugenics as a solution to crime.  Levitt states in his book Freakonomics that they are neither promoting nor negating any course of action - merely reporting data as economists.
See main article: Mexico City Policy. The Mexico City policy, also known as the "Global Gag Rule" required any non-governmental organization receiving US Government funding to refrain from performing or promoting abortion services in other countries. This had a significant effect on the health policies of many nations across the globe. The Mexico City Policy was instituted under President Reagan, suspended under President Clinton, reinstated by President George W. Bush, and suspended again by President Barack Obama on January 24, 2009. 
See main article: Religion and abortion.
See main article: Abortion law.
See also: Reproductive rights.
Before the scientific discovery in the nineteenth century that human development begins at fertilization, English common law forbade abortions after "quickening”, that is, after “an infant is able to stir in the mother's womb.” There was also an earlier period in England when abortion was prohibited "if the foetus is already formed" but not yet quickened. Both pre- and post-quickening abortions were criminalized by Lord Ellenborough's Act in 1803. In 1861, the British Parliament passed the Offences Against the Person Act, which continued to outlaw abortion and served as a model for similar prohibitions in some other nations.
The Soviet Union, with legislation in 1920, and Iceland, with legislation in 1935, were two of the first countries to generally allow abortion. The second half of the 20th century saw the liberalization of abortion laws in other countries. The Abortion Act 1967 allowed abortion for limited reasons in the United Kingdom. In the 1973 case, Roe v. Wade, the United States Supreme Court struck down state laws banning abortion, ruling that such laws violated an implied right to privacy in the United States Constitution. The Supreme Court of Canada, similarly, in the case of R. v. Morgentaler, discarded its criminal code regarding abortion in 1988, after ruling that such restrictions violated the security of person guaranteed to women under the Canadian Charter of Rights and Freedoms. Canada later struck down provincial regulations of abortion in the case of R. v. Morgentaler (1993). By contrast, abortion in Ireland was affected by the addition of an amendment to the Irish Constitution in 1983 by popular referendum, recognizing "the right to life of the unborn".
Current laws pertaining to abortion are diverse. Religious, moral, and cultural sensibilities continue to influence abortion laws throughout the world. The right to life, the right to liberty, the right to security of person, and the right to reproductive health are major issues of human rights that are sometimes used as justification for the existence or absence of laws controlling abortion. Many countries in which abortion is legal require that certain criteria be met in order for an abortion to be obtained, often, but not always, using a trimester-based system to regulate the window of legality:
Other countries, in which abortion is normally illegal, will allow one to be performed in the case of rape, incest, or danger to the pregnant woman's life or health. A few nations ban abortion entirely: Chile, El Salvador, Malta, Ireland and Nicaragua, although in 2006 the Chilean government began the free distribution of emergency contraception.  In Bangladesh, abortion is illegal, but the government has long supported a network of "menstrual regulation clinics", where menstrual extraction (manual vacuum aspiration) can be performed as menstrual hygiene.
In places where abortion is illegal or carries heavy social stigma, pregnant women may engage in medical tourism and travel to countries where they can terminate their pregnancy. In the USA, it is not unusual for women to travel from one state to another for reasons of termination of pregnancy.
The following information resources may be created by those with a non-neutral position in the abortion debate:
. Mary Lefkowitz. Maureen B. Fant. Women's life in Greece & Rome: a source book in translation. Johns Hopkins University Press. Baltimore. 1992. 0-8018-4474-6. 25373320. 2008-12-02.
. Margaret McLean. Cornelie Usborne. Gender and Crime in Modern Europe. Routledge. New York. 1999. 231. 1-85728-745-2. 186748539.
. William Blackstone. Amendment IX, Document 1. http://press-pubs.uchicago.edu/founders/documents/amendIXs1.html. Commentaries on the Laws of England. 1765. 1979. University of Chicago Press. Chicago. 5. 388.