Cite Your Sources

LRS in the Wild

See the Principle in Real Life

Take a look at the following political cartoon, in which a member of the audience criticizes a politician’s speech.

"Wikipedian Protester."
Munroe, Randall. "Wikipedian Protester." xkcd: A Web Comic of Romance, Sarcasm, Math, and Language. Web. 30 July 2012. Used according to Creative Commons License BY-NC 2.5.

Why does this audience member want a citation? Because it's no secret that politicians sometimes twist the truth, give us unreliable statistics, and even make up things to support their points. We don’t trust what politicians say when we can’t check their evidence. That’s why major newspapers run “Fact Checker” columns that check the “facts” offered by politicians—and they find that their facts are sometimes wrong.

Of course, it's tough to add footnotes or a bibliography to a political speech. But these things are expected on your papers. If you want your readers to trust you more than they trust politicians, you need to cite your sources.

See It in Writing

About See It in Writing

You can’t rely only on common knowledge when you make arguments in academic and professional settings. Readers expect you to use reliable evidence taken from reliable sources.

Readers can't know whether your source is reliable unless you cite it. When you cite sources, you help yourself and your readers in three ways:

Most importantly, when you cite your sources you give credit to those whose work you rely on, paying them back in a small way for helping you make your own argument more credible.

Academic and professional readers regularly check sources not only to make sure that evidence is convincing and accurate but also to use that evidence in their own arguments. Just as you can use the citations in your sources to find additional sources, so your readers can use yours. Accurate and complete citations keep writers honest, but more importantly they locate your work in a web of research that makes us all smarter.

Let’s look at a paragraph from a student’s paper written for an education class. The writer’s main claim is that child labor laws in the U.S. are focused on urban employment and ignore children in rural communities. In this paragraph, the writer presents a number of facts as evidence for her argument.

What to Look For

  • What information strikes you as common knowledge?
  • What information could you easily look up in a general reference book?
  • What information would you have trouble accepting without a citation?

Since the 19th century, the laws regulating child labor in the United States have increasingly limited the hours and types of work that children under age 16 can perform. Before the 19th century, there were no laws regulating child labor, and many children worked long hours in mines, factories, and farms. In 1836, Massachusetts passed the first law requiring children under 15 working in factories to attend school at least three months per year. This law did not limit the number of hours a child could work per day, however. In 1842, Massachusetts passed the first law limiting children’s work days to 10 hours per day. The first national regulation of child labor came in the Fair Labor Standards Act of 1938. Today, children may begin working as employees at age 14, so long as the job is not dangerous and does not interfere with their schooling. But relatively few American children work. Those that work mostly do so not to support their families but to supplement their spending money. Twenty-one percent of those in the lowest-income group held employee jobs when they were 14, compared with between 25 and 27 percent of those whose households had incomes in the three higher groups. Most of this is summer work: only 4 percent of 14-year-olds and 8 percent of 15-year-olds work more than 15 hours per week during the school year. But if child labor laws protect children working as employees, many children work off the books in family businesses, such as farms, which have fewer regulations. This work can be quite dangerous, and more than 200,000 minors suffer work-related injuries every year. Thus, while child labor regulation has changed drastically since the 19th century to protect a majority of American youths, a small number of young people continue to work long hours during the school semester, occasionally in dangerous conditions.

Click "next" to compare your analysis with ours.

What Most Readers Think

Generally, readers do not expect citations for information they think of as common knowledge. They also do not expect citations for dates or other discrete facts that can be found in reference works. But they do expect a citation for any information they could not have known without the writer’s help.

In judging when you need a citation, you have to make a separate decision about each piece of evidence. Here is the passage again with footnotes.

Click on each sentence to if most readers would want to see a citation.

Since the 19th century, the laws regulating child labor in the United States have increasingly limited the hours and types of work that children under age 16 can perform. Before the 19th century, there were no laws regulating child labor, and many children worked long hours in mines, factories, and farms. In 1836, Massachusetts passed the first law requiring children under 15 working in factories to attend school at least three months per year.1 This law did not limit the number of hours a child could work per day, however. In 1842, Massachusetts passed the first law limiting children’s work days to 10 hours per day.2 The first national regulation of child labor came in the Fair Labor Standards Act of 1938.3 Today, children may begin working as employees at age 14, so long as the job is not dangerous and does not interfere with their schooling. But relatively few American children work. Those that work mostly do so not to support their families but to supplement their spending money. Twenty-one percent of those in the lowest-income group held employee jobs when they were 14, compared with between 25 and 27 percent of those whose households had incomes in the three higher groups.4 Most of this is summer work: only 4 percent of 14-year-olds and 8 percent of 15-year-olds work more than 15 hours per week during the school year.5 But if child labor laws protect children working as employees, many children work off the books in family businesses, such as farms, which have fewer regulations.6 This work can be quite dangerous, and more than 200,000 minors suffer work-related injuries every year.7 Thus, while child labor regulation has changed drastically since the 19th century to protect a majority of American youths, a small number of young people continue to work long hours during the school semester, occasionally in dangerous conditions.


1 University of Iowa Labor Center and Center for Human Rights, “Child Labor in U.S. History,” Child Labor Public Education Project, http://www.continuetolearn.uiowa.edu/laborctr/child_labor/about/us_history.html (accessed July 14, 2009).

2 "Child Labor."

3 “Fair Labor Standards Act: Acts, Bills, and Laws, 1938-Present,” Travel and History, http://www.u-s-history.com/pages/h1701.html (accessed July 17, 2009).

4 United States Bureau of the Census, Report on the Youth Labor Force, 2000, http://www.bls.gov/opub/rylf/pdf/rylf2000.pdf.

5 Youth Labor Force, 17.

6 Youth Labor Force, 56-60.

7 The Child Labor Coalition, “Health, Education, and Labor and the Convention on the Rights of the Child Symposium,” http://www.dianahacker.com/resdoc/p04 _c08_s2.html (accessed July 22, 2009).

The Basic Principle

About The Basic Principle

In a Nutshell

You must cite your sources if you want readers to have confidence in your evidence—and also in you. In most academic and professional arguments you must cite:

The Principle

Readers expect you to cite your sources. When you do so, you show them that your evidence is more than vaguely-remembered ideas, details that you guessed about, or things that you simply made up. Citing your sources helps readers accept that your evidence is reliable and allows them to follow up on it for themselves. Citations also protect you from suspicion of plagiarism and give credit to those who collected the evidence.

In class papers, citations serve two purposes. First, they show your teacher that you understand how to find and use sources. But they also show that you are prepared to produce quality work at a higher academic or professional level. When you write a college paper, it’s likely that none of your readers will check up on your sources or use your bibliography to guide their own research. But one day you may have readers who want to build on your work. By using citations properly now, you show your teacher that you are prepared for a day when getting them right will matter a great deal.

You should cite your sources:

There are several different formats writers can use to cite sources, depending on their field. The four most common formats are:

Check with your teacher to find out which style you should use.

See How It Works

About See How It Works

Readers expect you to cite any information that you borrowed from a source and that is not common knowledge. When you cite sources, you give readers a way to follow up on your evidence, to check out how reliable it is, or just to learn more about it; you also give credit to the original author of the words or ideas. You'll lose your readers' trust quickly when they think you're taking credit for words or ideas that are not your own. This is commonly known as plagiarizing.

Readers expect you to cite a source every time you:

What to Look For

Let’s look at an example from a paper in an African history class. The writer claims that the biggest problem faced by African countries is access to basic health care. In this paragraph, the writer explains why the disease malaria causes so much devastation, even though it's inexpensive to prevent. We have removed all quotation marks and citations.

  • As you read, decide what information needs a source because it (1) is not common knowledge and (2) is not the kind fact that you can readily find in a reference source such as an encyclopedia.

The health divide between Africa and the West can be seen in access to simple preventions for malaria infection. Malaria was eliminated in the United States in the 1950s. Worldwide, malaria still causes the deaths of approximately 1 million people each year, mostly young children in Africa. Malaria causes not only suffering and many deaths, but also economic losses and poverty. The World Health Organization (WHO) estimates that malaria cuts economic growth rates by as much as 1.3% in countries with high disease rates. The economic losses are due to lost adult productivity, but also to lost years of education. According to Sue Mbaya, Director of World Vision's Africa program, malaria infection disrupts education at a crucial point: infected children often miss school and too many are burdened with long-lasting complications of anemia or brain damage, diminishing physical and mental productivity for years. Although the damage done by malaria is great, the cost of prevention can be as little as a few cents for insecticide-treated mosquito nets. The WHO states that the current supply of nets is sufficient to protect an estimated 26% of people in 37 African countries.

Click here to see this paragraph with quotation marks and citations.

The Principles At Work

As you can see, this paragraph offers a lot of information, most of which is not common knowledge that most readers would know or could find easily. It is unlikely, then, that readers would think that this student would know all these facts offhand. In fact, most people would agree that all of these facts are not at all widely known. Most readers would therefore expect to see this writer cite her sources, or they won't trust that she didn't just make this information up.

Here is the paragraph again with quotation marks and citations (in the form of footnotes). Notice how now the student uses a mixture of paraphrases, quotations, and citations to show her readers that she got her information from a reliable source.

Click on each segment for an explanation of why the writer provided a citation.

The health divide between Africa and the West can be seen in access to simple preventions for malaria infection. Malaria was eliminated in the United States in the 1950s. Worldwide, malaria still causes the deaths of approximately 1 million people each year, mostly young children in Africa.1 Malaria causes not only suffering and many deaths, but also economic losses and poverty. The World Health Organization (WHO) estimates that malaria “cuts economic growth rates by as much as 1.3% in countries with high disease rates.”2 The economic losses are due to lost adult productivity, but also to lost years of education. According to Sue Mbaya, Director of World Vision's Africa program, malaria infection disrupts education at a crucial point: “infected children often miss school and too many are burdened with long-lasting complications of anemia or brain damage, diminishing physical and mental productivity for years.”3 Although the damage done by malaria is great, the cost of prevention can be as little as a few cents for insecticide-treated mosquito nets. The WHO states that the current supply of nets will only protect about one quarter of people in 37 African countries.4


1Centers for Disease Control and Prevention. “Malaria.” http://www.cdc.gov/malaria/index.html.

2World Health Organization. “Malaria: Key Facts.” http://www.who.int/mediacentre/factsheets/fs094/en/.

3Sue Mbaya. “World Malaria Day: Here in Africa, Mosquitoes Still Kill.” The Huffington Post, April 24, 2009. http://www.huffingtonpost.com.world-vision/here-in-africa-mosquitoes_b_191187.html.

4World Health Organization. World Malaria Report 2008. WHO/HTM/GMP/ 2008.1. Geneva: WHO Press, 2008. http://www.who.int/malaria/publications/atoz/ 9789241563697/en/index.html.

The Core Concept

Good writing relies ultimately on evidence: facts that show readers that what they're saying is true. But readers don't just want to know the facts to be convinced that you're right; they also need to know where you got those facts. If they can't figure out where your evidence comes from, they will find it harder to trust that what you're saying is true.

Try It Out

About Try It Out

The following paper was written for a course in Latin American Studies. The writer was told to write a paper that explores collective rural uprisings in El Salvador based her paper on two academic books on the subject. There are two goals in this assignment: first, to demonstrate that she has read the two books thoughtfully and that she can create her own distinctive synthesis of their information; and second, to find a worthy question and develop a sound argument based on the evidence in the books.

Exercise 1

Read the following paragraph excerpted from this paper. Click each underlined section and decide if it needs a citation or not. Once you have answered a question, sections that need citations will be highlighted in blue, and sections that don't need citations will be highlighted in red.


Is a citation needed for this sentence?

Requires source citation.

Does not require source citation.


You said there was no citation needed. Correct. Since these two sentences present a reason that the rest of the paragraph supports with evidence and analysis, they do not require a citation. Reasons present the writer’s ideas and sub-claims that support the main claim—they should not be borrowed from another source. (However, if a reason includes quoted material or a specific fact that is not generally accepted, the quoted material or the fact will require source citation.)


You said there was a citation needed. Sorry. Since these two sentences present a reason that the rest of the paragraph supports with evidence and analysis, it does not require a citation. Reasons present the writer’s ideas and sub-claims that support the main claim—they should not be borrowed from another source. (However, if a reason includes quoted material or a specific fact that is not generally accepted, the quoted material or the fact will require source citation.)


You said there was no citation needed. Correct. This sentence summarizes and frames the material from an academic book that is quoted and cited in the next sentence. Since this is the writer’s framing, this sentence does not require source citation.


You said there was a citation needed. Sorry. This sentence summarizes and frames the material from an academic book that is quoted and cited in the next sentence. Since this is the writer’s framing, this sentence does not require source citation.


You said there was a citation needed. Correct. Quoted material always requires citation. Since this quoted material supports the summary in the preceding sentence, citing this quotation also anchors the preceding statement in specific evidence. Here is how the writer cites the source: The quotation is from the book titled Insurgent Collective Action and Civil War in El Salvador by Elisabeth Jean Wood (Cambridge: Cambridge Univ. Press, 2003). The book has already been referenced in the essay and cited in full in a "Works Cited" list at the end of the essay. To cite this specific quote, the writer follows the quotation with an in-text parenthetical: "(Wood 91)."


You said there was no citation needed. Sorry. Quoted material always requires citation. Since this quoted material supports the summary in the preceding sentence, citing this quotation also anchors the preceding statement in specific evidence. Here is how the writer cites the source: The quotation is from the book titled Insurgent Collective Action and Civil War in El Salvador by Elisabeth Jean Wood (Cambridge: Cambridge Univ. Press, 2003). The book has already been referenced in the essay and cited in full in a "Works Cited" list at the end of the essay. To cite this specific quote, she follows the quotation with an in-text parenthetical: "(Wood 91)."


You said there was no citation needed. Correct. This sentence summarizes and frames the material from an academic book that is quoted and cited in the next sentence. Since this is the writer’s framing, this sentence does not require source citation.


You said there was a citation needed. Sorry. This sentence summarizes and frames the material from an academic book that is quoted and cited in the next sentence. Since this is the writer’s framing, this sentence does not require source citation.


You said there was a citation needed. Correct. Quoted material always requires citation. And, since this quoted material supports the summary in the preceding sentence, citing this quotation also anchors the preceding statement in specific evidence. Here is how the writer cites the source: The quotation is from the book titled Insurgent Collective Action and Civil War in El Salvador by Elisabeth Jean Wood (Cambridge: Cambridge Univ. Press, 2003). The book has already been referenced in the essay and cited in full in a "Works Cited" list at the end of the essay. To cite this specific quote, the writer follows the quotation with an in-text parenthetical: "(Wood 90)."


You said there was no citation needed. Sorry. Quoted material always requires citation. And, since this quoted material supports the summary in the preceding sentence, citing this quotation also anchors the preceding statement in specific evidence. Here is how the writer cites the source: The quotation is from the book titled Insurgent Collective Action and Civil War in El Salvador by Elisabeth Jean Wood (Cambridge: Cambridge Univ. Press, 2003). The book has already been referenced in the essay and cited in full in a "Works Cited" list at the end of the essay. To cite this specific quote, the writer follows the quotation with an in-text parenthetical: "(Wood 90)."


You said there was no citation needed. Correct. This sentence summarizes and frames the material from an academic book that is quoted and cited in the next sentence. Since this is the writer’s framing, this sentence does not require source citation.


You said there was a citation needed. Sorry. This sentence summarizes and frames the material from an academic book that is quoted and cited in the next sentence. Since this is the writer’s framing, this sentence does not require source citation.


You said there was a citation needed. Correct. Quoted material always requires citation. And, since this quoted material supports the summary in the preceding sentence, citing this quotation also anchors the preceding statement in specific evidence. In general, an author should not only provide a source citation for the larger quotation but also for the quotation within the quotation, which Wood cites in her book. Here is how the writer cites the source: The quotation is from the book titled Insurgent Collective Action and Civil War in El Salvador by Elisabeth Jean Wood (Cambridge: Cambridge Univ. Press, 2003). The book has already been referenced in the essay and cited in full in a "Works Cited" list at the end of the essay. To cite this specific quote and to clarify that the quotation is from another source that Wood cites, the writer follows the quotation with an in-text parenthetical: "(Wood 97; the woman’s statement was obtained by Wood in an interview she conducted in Tenancingo in 1987)."


You said there was no citation needed. Sorry. Quoted material always requires citation. And, since this quoted material supports the summary in the preceding sentence, citing this quotation also anchors the preceding statement in specific evidence. In general, an author should not only provide a source citation for the larger quotation but also for the quotation within the quotation, which Wood cites in her book. Here is how the writer cites the source: The quotation is from the book titled Insurgent Collective Action and Civil War in El Salvador by Elisabeth Jean Wood (Cambridge: Cambridge Univ. Press, 2003). The book has already been referenced in the essay and cited in full in a "Works Cited" list at the end of the essay. To cite this specific quote and to clarify that the quotation is from another source that Wood cites, the writer follows the quotation with an in-text parenthetical: "(Wood 97; the woman’s statement was obtained by Wood in an interview she conducted in Tenancingo in 1987)."

The Catholic Church and liberation theology played a prominent role in the insurgence against the government in El Salvador. Liberation theology—the theory that Jesus Christ preached political resistance to unjust governments—took deeper root in rural communities in part because of specific methods of community outreach and organization practiced by the Church. First, Jesuit missionaries and seminarians had prolonged visits in various rural areas, as a means to spread liberation theology and to recruit new missionaries. Starting in 1972, they “liv[ed] for two weeks in each cantón of the parish, visiting and eating with families and recruiting catechists who participated in short training courses that emphasized group reflection on the structures of sin, violence, and oppression.” Second, Bible study groups in northern cantones integrated Biblical studies into political efforts to organize agrarian insurgent groups. “Some residents of the northern cantones who became participants in the insurgency began by joining Bible study groups organized by Catholic priests and catechists.” The integration of religious and political forces is demonstrated in part by how military forces focused on churches. A Villa woman told Wood in an interview that “They [the guardsmen] threatened church-goers. People continued going to church, but fearfully. Even the priest was questioned by the soldiers.”

Exercise 2

Now, let’s take a look at a paragraph from the book that the writer cites often in her paper: Insurgent Collective Action and Civil War in El Salvador by Elisabeth Jean Wood (Cambridge: Cambridge Univ. Press, 2003). Remember that the context of a piece of writing—both for whom or what it is written and the level of expertise that the piece is expected to reflect—helps to determine the level of citation that is required.

Click each underlined section and decide if it needs a citation or not. Once you have answered a question, sections that need citations will be highlighted in blue, and sections that don't need citations will be highlighted in red.


Is a citation needed for this sentence?

Requires source citation.

Does not require source citation.


You said there was a citation needed. Correct. Wood attributes this information to a source, Carlos Rafael Cabarrús, so she must provide a citation. Also, the phrase "unblocking" is likely a quotation, and thus needs to be cited. Here is the published parenthetical citation:
"(Cabarrús 1985: 135)." The full citation is available in a "References" section at the end of the book; since Wood is using a social-science citation style, her parenthetical citation provides the author’s last name, the year of publication, and the page number.


You said there was no citation needed. Sorry. Wood attributes this information to a source, Carlos Rafael Cabarrús, so she must provide a citation. Also, the phrase "unblocking" is likely a quotation, and thus needs to be cited. Here is the published parenthetical citation: "(Cabarrús 1985: 135)." The full citation is available in a "References" section at the end of the book; since Wood is using a social-science citation style, her parenthetical citation provides the author’s last name, the year of publication, and the page number.


You said there was a citation needed. Correct. Quoted material always requires citation. Here is the published parenthetical citation: "(Cardenal 1985: 259)." The full citation is available in a "References" section at the end of the book; since Wood is using a social-science citation style, her parenthetical citation provides the author’s last name, the year of publication, and the page number.


You said there was no citation needed. Sorry. Quoted material always requires citation. Here is the published parenthetical citation: "(Cardenal 1985: 259)." The full citation is available in a "References" section at the end of the book; since Wood is using a social-science citation style, her parenthetical citation provides the author’s last name, the year of publication, and the page number.


You said there was a citation needed. Correct. Quoted material always requires citation. Here is the published parenthetical citation: "(ibid.: 261)." The full citation is available in a "References" section at the end of the book; "ibid" means "in the same place," that is, the same source as the preceding source; a different page number is given.


You said there was no citation needed. Sorry. Quoted material always requires citation. Here is the published parenthetical citation: "(ibid.: 261)." The full citation is available in a "References" section at the end of the book; "ibid" means "in the same place," that is, the same source as the preceding source; a different page number is given.


You said there was a citation needed. Correct. Quoted material always requires citation. Here is the published parenthetical citation: "(ibid.: 272)." The full citation is available in a "References" section at the end of the book; "ibid" means "in the same place," that is, the same source as the preceding source; a different page number is given.


You said there was no citation needed. Sorry. Quoted material always requires citation. Here is the published parenthetical citation: "(ibid.: 272)." The full citation is available in a "References" section at the end of the book; "ibid" means "in the same place," that is, the same source as the preceding source; a different page number is given.


You said there was no citation needed. Correct. In this sentence, Woods provides her own analytical synthesis of the previous material in the paragraph. It presents a reason in support of a larger argument. We form reasons inside our own minds: they are explanatory statements that we want a reader to accept as true about our evidence, so they do not require source citation. (However, if the written reason includes quoted material or a specific fact that is not generally accepted, the quoted material or the fact will require source citation.)


You said there was a citation needed. Sorry. In this sentence, Woods provides her own analytical synthesis of the previous material in the paragraph. It presents a reason in support of a larger argument. We form reasons inside our own minds: they are explanatory statements that we want a reader to accept as true about our evidence, so they do not require source citation. (However, if the written reason includes quoted material or a specific fact that is not generally accepted, the quoted material or the fact will require source citation.)

According to Carlos Rafael Cabarrús, a Guatemalan Jesuit and anthropologist who was part of the Aguilares pastoral team, this new style of pastoral work with its emphasis on history and liberation caused an “unblocking” of traditional campesino fatalism. Another Jesuit analyst of the Aguilares experience observed that catechists and some other parishioners “realized that it was not the will of God that things continue unchanged. In effect, the mission’s preaching had lowered God from the clouds and presented him as Yahweh, God of history.” As a result, many actively committed themselves to work for justice and peace, even if it meant giving their lives: “[T]he absolute ‘No’ of God toward injustice demanded as well a ‘Yes’ toward justice and peace.” The priests explicitly denounced injustices from the pulpit and recorded the abusive harvest practices of local landlords. As parishioners increasingly identified with “Jesús Rebelde” (Rebel Jesus), their gathering refusal “to accept present inequality in exchange for equality after death” broke the dominant ideology. Participants began to develop a new confidence in themselves as they discovered their ability to develop and express opinions in public and a new solidarity among themselves in place of their traditional identification with the patrón.