Skip to main content

Chemical Weapons

CHEMICAL WEAPONS

Chemical Weapons (CWs) constitute a major but often under appreciated ethical and political challenge for science and technology. The following entry examines this challenge by describing the character of CWs, the history of their use, and efforts of ethical and political control.



Chemical Weapons: What Are They?

Definitions of chemical warfare and chemical weapon have changed over time. History is replete with examples of chemicals being employed either to kill individuals, for example, murder or assassination, or larger numbers during warfare, such as the use of Greek Fire (a mixture of petroleum, pitch, sulfur, and resins) during at least two sieges of Constantinople (673 and 718 c.e.) However the twenty-first-century understanding of CWs is based on a better scientific appreciation of the underlying chemical and biological processes involved, which began to take shape during the nineteenth century.

Knowledge of how the toxic properties of chemicals could be employed as a method of warfare evolved in conjunction with the industrial and scientific infrastructure that brought about the large-scale production of chemicals. Such an infrastructure provided equipment, production protocols, and analytical techniques from the chemical industry and its research laboratories for CW purposes. Prior to such developments chemical warfare was essentially poisoning by persons who had little or no understanding of how such weapons functioned.

The internationally accepted definition of chemical weapons is that contained in the 1993 Chemical Weapons Convention (CWC), which states that such weapons consist of one or more of three elements: (a) toxic chemicals and their precursors (the chemicals used in the synthesis of the toxic chemicals) when intended for warfare; (b) munitions and devices specifically designed to cause harm or death through the use of such toxic chemicals; or (c) any equipment specifically designed to be used directly in connection with such chemicals, munitions, and devices.

Note the presence of a chemical in munitions does not automatically make them CWs. Weapons containing napalm and white phosphorus, for example, are not CWs because their primary effect depends on the incendiary properties of these chemicals and not their toxicity. The CWC definition of CWs contains a general purpose criterion (GPC) that bans the production and use of all toxic chemicals except for peaceful purposes.

The GPC is the principal mechanism by which technological and scientific developments can be taken into account by the Organisation for the Prohibition of Chemical Weapons (OPCW), which implements the CWC. The CWC definition of CWs is also phrased to ensure that bulk CW storage containers, and binary or other multi-component systems are covered by the convention.

Finally, toxins—the highly toxic chemical byproducts produced by certain types of living organisms—are covered by both the 1972 Biological and Toxin Weapons Convention (BTWC) and the CWC. Thus the use of a toxin as a method of warfare or for hostile purposes may be legally defined as both chemical and biological warfare.

Although CWs are, together with nuclear, biological, and radiological weapons, often referred to as weapons of mass destruction, they vary widely in terms of effect and lethality. While some CW agents are highly dangerous (i.e., toxic), others were developed to be used as incapacitatants (e.g., BZ or 3-quinuclydinyl benzilate, a hallucinogenic drug).

In terms of killing power, CW agents are not in the same category as nuclear weapons and some biological warfare agents. A fuel-air explosive, or thermobaric device, is generally more lethal (and predictable) than a comparable payload of CW agents. Comparisons are further complicated if one considers low-yield nuclear warheads, such as those being developed for use as part of deep-penetrating munitions, or bunker busters. Such weapons could be used in a manner that results in the deaths of only those people located inside a targeted, deeply buried and/or hardened facility.

Finally, LD50 (the amount of agent required to cause 50 percent of those targeted to die) figures do not reflect practical problems associated with the delivery to target of CW agents. The estimated amounts of agent required to effectively contaminate a given area help to illustrate such problems and, therefore, the actual threat posed to individuals by CW agents in the field.

Great attention has been given to the development of firing tables for various types of munitions and agents. For example, a U.S. Army manual estimates that approximately twenty-seven kilograms must be used to achieve a single casualty among protected troops. It has also been estimated that four metric tons of the organophosphorus nerve agent VX would be required to contaminate effectively a six-square-kilometer area. The equivalent figures for CWs employed in enclosed, urban areas, are generally somewhat lower. Additional uncertainties are caused by problems associated with extrapolating research data from various test animals to humans and extrapolating data involving the use of simulants, rather than actual CW agents, particularly in field tests.

CW agents may be divided according to their principal physiological effects: blister or vesicant, blood, choking, incapacitating, nerve, tear gas, and vomiting agents. Vesicants cause skin blisters and can cause severe damage to the eyes, throat, and lungs. Life-threatening infections in the trachea and lungs may result. Lewisite (L), nitrogen mustards (HN-1, HN-2, HN-3), sulfur mustard (H, HD), and phosgene oxime (CX) are examples of blister agents. Their primary purpose is to cause mass casualties requiring intensive, long-term treatment, rather than death. Those exposed may also suffer long-term health problems, such as cancer.

Blood agents, such as arsine (SA), cyanogen chloride (CK), and hydrogen cyanide (AC), inhibit cytochrome oxidase, an enzyme needed to allow oxygen to be transferred from the blood to body tissue and, in the case of significant exposure, rapidly become fatal.

Choking agents, such as chlorine, diphosgene (DP), and phosgene (CG), interfere with breathing. Phosgene and diphosgene interfere with transfer of oxygen via the lung's alveoli sacks. Symptoms of phosgene poisoning do not become apparent for several hours. In addition the chances for survival are a function of physical exertion. The more strenuously victims exert themselves physically after exposure, the more likely they are to die. Complete rest and oxygen treatment are recommended.

Incapacitating agents are designed to induce physical disability or mental disorientation. LSD (a form of lysergic acid) and BZ (3-quinuclidinyl benzilate) are two examples. The United States investigated the potential military uses of LSD. It also weaponized BZ, which can cause constipation, headaches, hallucinations, and a slowing of mental thought processes.

The principal nerve agents, sarin (GB), cyclosarin (GF), soman (GD), tabun (GA) and V-agents, are all organophosphorus compounds that inhibit an enzyme responsible for breaking down acetylcholine, a neurotransmitter. Nerve agents may be inhaled or absorbed through the skin. Symptoms include drooling, dilated pinhead pupils, headache, involuntary defecation, and a runny nose. Death is caused by cardiac arrest or respiratory failure.

Tear gases, such as chloroacetephenone (CN) and O-chlorobenzalmalonitrile (CS), cause irritation of the skin and uncontrolled tearing. Although these are designed to be used as non-lethal, riot control agents, their employment can result in death or injuries if improperly used in enclosed areas or for extended periods of time that results in high levels of exposure.

Although vomiting agents, such as adamsite (DM), diphenylchloroarsine (DA), and diphenylcyanoarsine (DC), have been used for riot control purposes, in the early twenty-first century they are generally considered too toxic for this purpose. All three agents have become obsolete as CWs against an opponent using modern protective equipment. Diphenylchloroarsine and diphenylcyanoarsine, which are in the form of a powder at normal ambient temperatures, were used as mask breakers during World War I and by the Japanese in China (1937–1945). The particles were able to penetrate the filters used at the time and could induce a soldier to break the seal of his mask allowing a more toxic agent such as phosgene to take effect. Diphenylchloroarsine and diphenylcyanoarsine were also mixed with sulfur mustard to lower the freezing temperature of the mustard and thus allow the mixture to be used at lower ambient temperatures.



History of Chemical Weapon Use

The first use of a chemical for lethal effect in modern times occurred on April 22, 1915, when the German army released approximately 180 tons of liquid chlorine at Ypres, Belgium, resulting in the deaths of an estimated 5,000 Algerian, Canadian, and French soldiers. The widest variety of chemical compounds developed and used on a large-scale are found among the CW agents produced during this conflict. At least forty different compounds were weaponized. But the most significant development was the production of sulfur mustard. This was first used at the second battle of Ypres in 1917 and, by the end of the war, had become known as the king of war gases due to the very large number of casualties resulting from its use. An estimated 1.45 billion shells were fired during the war, of which approximately 66 million contained CW-fill. Approximately 3,500 to 4,000 World War I-era shells were still being recovered annually in Europe during the 1990s, mostly in Belgium and France, of which about 10 to 20 percent are CWs.

Following the widespread use of CWs during World War I, countries with significant military capabilities or security concerns were compelled to consider threats that known or yet-to-be-discovered toxic chemicals might pose, particularly if delivered against vulnerable urban areas by aircraft (or balloons). During World War II, even larger stocks of CWs were produced and stockpiled than in World War I. Despite their widespread availability, however, CWs were, in general, not used during World War II. Most of the stockpiled CWs were either destroyed or disposed of by sea dumping at the end of the war. Their residue is the source of an old CW problem that continues to occur in a number of countries worldwide.

Military establishments have generally been reluctant to embrace chemical weapons, partly out of moral considerations. The use of CWs has generally gone against military codes of conduct. Their use was also generally viewed as an unnecessary complicating factor in military planning and practice operations. This was because of an inability to reliably predict lethal or casualty-causing effects. CW agents may quickly degrade or be dissipated by environmental factors such as rain, heat, and wind. Care must also be taken to ensure that the explosive charge for a CW munition can effectively disperse the agent, without destroying too much of the agent in the process. Aerosol platforms, mainly slow, low-flying aircraft, are also vulnerable to attack. Finally, modern protective clothing, if properly used and maintained, is generally effective against known CW agents.

There have been allegations of the use of CWs during most major armed conflicts in the twentieth century. Many allegations are unproven and appear to be false. This is partly due to deliberate misinformation, information indicating that an opponent possesses CWs or is pursuing a CW program, and the fact that participants may mistake toxic fumes generated during battle as CWs (for instance, fumes generated from the detonation of high explosives). From the early 1980s to the early 1990s, the United Nations Secretary-General investigated allegations of the use of chemical and biological weapon agents in Africa, Armenia, Iran, Iraq, and southeast Asia. The authority of the Secretary-General remains in effect. However if the alleged use were with CWs, the CWC would almost certainly take legal precedence. As previously noted, however, toxins are covered by both the BTWC and the CWC.

CW agents were used by British forces intervening in Russia's Civil War in 1919 (for example, adamsite), by Spain in Morocco in 1924 to 1927 (sulfur mustard), by Italian forces in Abyssinia in 1935 to 1940 (sulfur mustard, phosgene, phenyldichlorarsine), by Japanese forces in Manchuria in 1937 to 1945 (lewisite, diphenyl cyanoarsine, sulfur mustard), by Egypt in the Yemen civil war in 1963 to 1967 (sulfur mustard and phosgene), and by Iraq against Iran in 1982 to 1988 (cyclosarin, sulfur mustard, sarin, and tabun). The use of tear gas by U.S. forces as part of combat operations in Vietnam (to clear tunnel systems, for example) is also generally considered to be an instance of chemical warfare. The CWC forbids the use of riot control agents as a method of warfare. The use of tear gases as part of combat operations is therefore prohibited.

During the Iran-Iraq War (1980–1988), Iraq used CWs, including sulfur mustard and nerve agents (cyclosarin, sarin, tabun) extensively against Iran and its own Kurdish population. Although allegations have been made that Iran used CWs against Iraq, they have not been conclusively proven. By contrast, investigative teams sent to the region during the war by the U.N. Secretary-General conclusively proved Iraqi use of CWs. Iran is a party to the CWC and has declared a past production capability, but has not declared a CW stockpile.

Following the 1991 Persian Gulf War, the U.N. Security Council adopted resolution 687 of 1991 which, inter alia, required Iraq to end its CW program and destroy its CW stockpiles. The resolution also established the U.N. Special Commission on Iraq (UNSCOM) to verify the destruction and dismantlement of prohibited weapons and associated programs. (The International Atomic Energy Agency, or IAEA, was given primary responsibility for overseeing the nuclear weapon disarmament of the country.) The principal CW agents produced by Iraq were cyclosarin, sarin, sulfur mustard, and tabun, while the main unresolved CW issue was the nature and extent of Iraq's VX program. Iraq claimed that it had never weaponized VX and had only produced limited, pilot plant-scale quantities of the agent (2–3 metric tons of poor quality material). UNSCOM disputed this claim. UNSCOM inspectors left Iraq in late 1998, as a consequence of a dispute partly based on whether UNSCOM inspectors should be allowed unrestricted access to so-called presidential sites, with the VX issue still unresolved. In December 1999, UNSCOM was replaced by the United Nations Monitoring, Verification and Inspection Commission (UNMOVIC) (U.N. Security Council resolution 1284 of 1999). UNMOVIC conducted its first inspections of Iraq on November 27, 2002, partly under the terms of UN Security Council resolution 1441 of 2002, which deplored Iraq's failure to fully disclose all aspects of its prohibited programs, including with respect to CWs. In describing the nature of Iraqi cooperation with UNMOVIC inspectors, the UNMOVIC Executive Chairman made a distinction between substance and process. While Iraq did provide immediate access to all requested sites, its active and full cooperation was questioned. Another major unresolved CW issue was the failure by Iraq to account for approximately 6,500 munitions filled with about 1,000 metric tons of chemical agent. As of September 10, 2003, there were no reports of any CWs having been recovered by the U.S.-U.K.-led coalition forces that entered Iraq in March 2003.

The most significant use of CWs by a non-state actor was carried out by the Japanese-based religious cult Aum Shinrikyo. The first major lethal attack occurred in June 1994 when cult members vented sarin vapor from a specially modified van at night in Matsumoto, Japan, outside the homes of three judges who were then involved in a legal case involving the organization. Seven people died and approximately 300 were injured as a result. The incident was not immediately recognized as a CW attack and the police investigation was indecisive and poorly coordinated.

The second attack occurred in March 1995 when group members released sarin in the Tokyo subway. As a result, twelve people died, while approximately 500 people required medical attention or hospitalization. Approximately 5,500 people were examined. In this case, the means of attack and the identity of the perpetrators were quickly determined and the police carried out mass arrests and widespread searches of properties owned by the cult.

At the time, the group had assets worth an estimated 1 billion U.S. dollars. A number of cult members had masters and doctorate degrees in the natural sciences, including chemistry. Despite these factors, Aum Shinrikyo technical ability in creating chemical (and biological) warfare agents was limited. The sarin produced, for example, was unstable and of low purity. Safety precautions during testing and production were poor and a number of cult members were poisoned as a result. In 2004 the cult's founder and head, Chizuo Matsumoto (a.k.a. "Shoko Asahara" or "bright light"), was sentenced to death.



Attempt at Ethical and Political Control

Agreements regarding CWs include the International Declaration Concerning the Laws and Customs of War (Brussels Conference, 1874); the Acts signed at the First International Peace Conference, Annex to the Convention (The Hague 1899); the Acts signed at the Second International Peace Conference, Annex to the Convention (The Hague 1907); the Treaty of Peace with Germany (also known as the Treaty of Versailles 1919); and the Treaty of Washington of 1922 Relating to the Use of Submarines and Noxious Gases in Warfare (Washington, DC 1922).

A more significant international legal instrument was the Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare, the well-known Geneva Protocol of 1925. The Geneva Protocol did not, however, prevent the stockpiling of CWs and many of the major powers attached conditions to their instruments of ratification (such as, that a state would not consider itself bound by treaty obligations if first attacked with CWs or if involved in a military conflict with states not party to the Protocol or military coalitions which included one or more states not Party to the Protocol).

Since 1993, however, the main international legal instrument dealing with CWs is the CWC. Treaty negotiations began in 1968 within the framework of the U.N. Eighteen-Nation Committee on Disarmament (the present-day Conference on Disarmament).

The CWC is implemented by the OPCW, based in The Hague, Netherlands. The OPCW consists of three parts: The Conference of the States Parties (CSP), the Executive Council (EC), and the Technical Secretariat (TS). The CSP is composed of all member states. It is the highest decision-making body and meets in regular session once each year. The EC is a representative body composed of forty-one members that represent five regional groups (Africa, Asia, Eastern Europe, Latin America and the Caribbean), and Western Europe and other states. Its main task is to oversee operational aspects of treaty implementation. It meets in regular session three to four times each year. Special sessions of the CSP and EC may be convened if a request (made by one or more parties) to convene is supported by at least one-third of the members. A special session of the EC would be convened, for example, if CWs were used. The TS is responsible for the practical implementation of the OPCW, including the processing of annual declarations submitted to the OPCW by the parties and the carrying out of on-site inspections. It has a staff of approximately 485, including about 200 inspectors. The OPCW's budget for 2003 was 68,562,966 euros.

As of July 7, 2003, 153 countries had ratified or acceded to the CWC, while twenty-five countries had signed but not ratified the convention and sixteen countries had neither signed nor ratified the convention. The OPCW's budget for 2004 was 73,153,390 euros. As of March 31, 2004, 161 countries had acceded to the CWC, while twenty countries had signed but not acceded the convention and twelve countries had neither signed nor acceded to the convention. Most of the non-member states are located in Africa or the Middle East, including Iraq, Israel, Egypt, and Syria. Many Arab countries have linked their accession to the CWC to Israel's becoming party to the 1972 Non-Proliferation Treaty (in doing so, Israel would have to demonstrate that it does not possess nuclear weapons). India, Iran, and Pakistan are parties to the CWC.

There are three principal types of inspections under the CWC: routine inspections, challenge inspections, and investigations of alleged use of CWs. CW-related facilities, including CW destruction facilities and facilities that use small quantities of agent for protective purposes, must be declared and are subject to routine on-site inspections. Part of the chemical industry, which processes, produces, or consumes certain chemicals above certain thresholds must also be declared and are subject to inspection. Thus far there have been no challenge inspections or investigations of alleged CW use. The CWC regime has provided a forum in which the parties can consider the contents of each others' declarations and pursue informally further clarification through informal consultations.

The CWC requires that all state parties declare whether they have produced CWs at any time since January 1, 1946. As of March 2004, twelve parties (Bosnia and Herzegovina, China, France, India, Iran, Japan, Libya, South Korea, Russia, the United Kingdom, the United States, and the former Yugoslavia (now Serbia and Montenegro) had declared sixty-four CW production facilities or sites. As of the same date ten parties (Australia, Belgium, Canada, France, Germany, Italy, Japan, Slovenia, the United Kingdom, and the United States) had declared possessing old CWs (defined as CWs produced before 1925, or between 1925 and January 1, 1946, and which have been determined not to be usable) and three parties (China, Italy and Panama) have declared having abandoned CWs (defined as CWs abandoned by a state on the territory of another state without the permission of the latter).

The CWC is a cooperative regime designed to allow member states to demonstrate their treaty compliance to each other. For such inspections to be completely successful, inspected states must cooperate. If they do not, inspectors should nevertheless be able to acquire some useful information or results. At a minimum, the inspection should serve to provide sufficient information to enable the EC and CSP to formally decide on issues of compliance (for instance, non-cooperation). Under the terms of the CWC, inspected parties may invoke managed access provisions to protect sensitive information, including sensitive information about its chemical industry and information sensitive for national security reasons. The burden of satisfying the compliance concern nevertheless lies with the inspected party.

UNSCOM and UNMOVIC, by contrast, were provided mandates that were established as part of an agreement to end military hostilities between Iraq and U.N.-sanctioned, international coalition forces. As such UNSCOM and UNMOVIC were to be provided with unrestricted, immediate access to all requested sites. Their work was also backed by the implicit (or explicit) threat of military action and economic sanctions. If a case of continued, fundamental non-compliance with the CWC were to occur, the OPCW would refer the matter to the U.N. Security Council and U.N. General Assembly for their consideration and action.



Current and Future Trends and Challenges

In the early twenty-first century there is an increased emphasis on ensuring that non-state actors, such as terrorist groups, do not acquire or use CWs. Much of this effort is of a law enforcement or intelligence nature and thus classified or otherwise not openly discussed. There has also been an increased emphasis on harmonizing and strengthening export control regulations and preparing emergency response and management. This is reflected in increased efforts by the OPCW to achieve better uniformity in the collection and reporting of information to the organization, including on the transfers of certain chemicals that appear in the CWC Annex on Chemicals. The OPCW is also implementing a "plan of action" to ensure that the parties have established effective national implementing legislation. The plan has the active political support and engagement of the members.

A number of factors complicate the confirmation or verification of non-production of CWs in chemical industry facilities. In the late twentieth and early twenty-first centuries there was a shift in the size and flexibility of many chemical industry facilities, away from big (e.g., petrochemical) plants that produce large volumes of a limited number of chemicals using a dedicated production method and toward small facilities capable of manufacturing a wide variety of specialized chemicals to order on short notice using smaller, less polluting and more easily reconfigured equipment for different productions routes.

Twenty-first century scientific capabilities also caused a blurring of the distinction between chemical and biological processes. Many biological substances that could not previously be synthetically manufactured may be chemically engineered through such advanced technology. Most biological warfare agents could, in fact, be viewed as chemicals because their action is biochemical in nature and because the derivation of many biological agents involves manufacturing processes—as opposed, for example, to the extraction of substances from naturally occurring organisms. Finally, the manner in which new toxic chemicals are developed and synthesized has been revolutionized through, for example, advances in combinatorial and computational chemistry and microarray processing technologies.

Complete security against CWs will not be achieved. In view of human, financial, and other resource limitations, the approach taken to identify and respond to possible risks posed by CWs should be carefully considered and balanced. The effectiveness of national and international laws against the development and use of CWs is dependent on the amount of attention and resources countries elect to devote to the matter. Any decisions taken with regard to protecting against CWs should be based on the recommendations and experience of CW technical specialists.


JOHN HART

SEE ALSO Biological Weapons; Just War; Military Ethics; Terrorism; Weapons of Mass Destruction.

BIBLIOGRAPHY

Dando, Malcolm. (2001). The New Biological Weapons: Threat, Proliferation, and Control. Boulder, CO; Lynne Rienner.

Sidell, Frederick R.; Ernest T. Takafuji; and David Franz, eds. (1997). Medical Aspects of Chemical and Biological Warfare. Washington, DC: Borden Institute.

Lundin, S. Johan, ed. (1988). Non-Production by Industry of Chemical-Warfare Agents: Technical Verification under a Chemical Weapons Convention. Oxford: Oxford University Press.

Lundin, S. Johan, ed. (1991). Verification of Dual-Use Chemicals under the Chemical Weapons Convention: The Case of Thiodiglycol. Oxford: Oxford University Press.

Pechura, Constance M., and David P. Rall, eds. (1993). Veterans at Risk: The Health Effects of Mustard Gas and Lewisite. Washington, DC: National Academy Press.

Stockholm International Peace Research Institute. (1971–1975). The Problem of Chemical and Biological Warfare. 6 vols. Stockholm: Almqvist & Wiksell.

Trapp, Ralf. (1993). Verification under the Chemical Weapons Convention: On-Site Inspection in Chemical Industry Facilities. Oxford: Oxford University Press.

Tu, Anthony T. (2002). Chemical Terrorism: Horrors in Tokyo Subway and Matsumoto City. Fort Collins, CO: Alaken, Inc.


INTERNET RESOURCES

Organisation for the Prohibition of Chemical Weapons. Available from http://www.opcw.org.

United Nations Monitoring, Verification and Inspection Commission. (2003). "Unresolved Disarmament Issues: Iraq's Proscribed Weapons Programmes." UNMOVIC working document. Available from http://www.unmovic.org under heading "Cluster Document."

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"Chemical Weapons." Encyclopedia of Science, Technology, and Ethics. . Encyclopedia.com. 20 Sep. 2018 <http://www.encyclopedia.com>.

"Chemical Weapons." Encyclopedia of Science, Technology, and Ethics. . Encyclopedia.com. (September 20, 2018). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/chemical-weapons

"Chemical Weapons." Encyclopedia of Science, Technology, and Ethics. . Retrieved September 20, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/chemical-weapons

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.