A citation is a reference to a published or unpublished source that you consulted and obtained information from while writing your research paper. The way in which you document your sources depends on the writing style manual your professor wants you to use for the class [e.g., APA, MLA, Chicago, Turabian, etc.]. Note that some disciplines have their own citation method [e.g., law].
Citations show your readers where you obtained your material, provides a means of critiquing your study, and offers the opportunity to obtain additional information about the research problem under investigation.
Properly citing the works of others is important because:
Proper citation allows others to locate the materials you used. Citations to other sources help readers expand their knowledge on a topic. In some disciplines, one of the most effective strategies for locating authoritative, relevant sources is to follow footnotes or references from known sources ["citation tracking"].
Citing other people's words and ideas indicates that you have conducted thorough review of the literature on your topic and, therefore, you are operating from an informed perspective. This increases your credibility as the author of the work.
Other researchers' ideas can be used to reinforce your arguments, or, if you disagree with them, can act as positions from which to argue an alternative viewpoint. In many cases, another researcher's arguments can act as the primary context from which you can emphasize a different viewpoint or clarify the importance of what you are proposing.
Just as other researchers' ideas can bolster your arguments and act as evidence for your ideas, they can also detract from your credibility if they are found to be mistaken or fabricated. Properly citing information not unique to you prevents your reputation from being tarnished if the facts or ideas of others are proven to be inaccurate or off-base.
Outside academe, ideas are considered intellectual property and there can serious repercussions if you fail to cite where you got an idea from. In the professional world, failure to cite other people's intellectual property ruins careers and reputations and can result in legal action. Given this, it is important to get into the habit of citing sources.
In any academic writing, you are required to identify for your reader which ideas, facts, theories, concepts, etc., are yours and which are derived from the research and thoughts of others. Whether you summarize, paraphrase, or use direct quotes, if it's not your original idea, the source needs to be acknowledged. The only exception to this rule is information that is considered to be common knowledge [e.g., George Washington was the first president of the United States]. If in doubt regarding whether something is common knowledge, take the safe route and cite it, or ask your professor for clarification.
Citing Information. The Writing Center. University of North Carolina; Referencing More Effectively. Academic Skills Centre. University of Canberra.
Referencing your sources means systematically showing what information or ideas you are quoting or paraphrasing from another author’s work, and where they come from. You must cite research in order to do research, but at the same time, you must indicate what are your original thoughts and ideas and what are the thoughts and ideas of others.
Systems used to reference the sources you've used vary among different fields of study. However, always speak with your professor about what writing style for citing sources should be used for the class because it is important to fully understand the citation style to be used in your paper, and to apply it consistently.
GENERAL GUIDELINES
Should I avoid referencing other people's work? No! Referencing other people's work is never an indication that your work is poor or lacks originality if placed in the proper context. In fact, the opposite is true. If you write your paper with no references to previous research, you are indicating to the reader that you are not familiar with the research that has already been done, thereby undermining your credibility as an author and the validity of your research. Including references in academic writing is a way of demonstrating your knowledge of pertinent literature about the research problem.
What should I do if I find that my idea has already been published by another researcher? Acknowledge the other researcher's work by writing in your reference something like this: [see also Smith, 2002]. Do not ignore another author's work because doing so will lead your readers to believe that you have either taken the idea or information without properly referencing it [this is plagiarism] or that you have failed to conduct a thorough review of the literature in your field.
What should I do if I want to use an adapted version of someone else's work? You still must cite the original work. For example, maybe you are using a table of statistics from a journal article published in 1996 by author Smith, but you have altered or added new data to it. Reference the revised chart as: [adapted from Smith, 1996]. You can also use other terms in order to specify the exact relationship between the source and the version you have presented, such as, based on Smith [1996], summarized from Smith [1996], etc.
What should I do if several authors have published very similar information or ideas? You can indicate that the idea or information can be found in the work of more than one author, by stating something like: "Though in fact many authors have applied this theory to understanding economic relations among nations [for example, Smith, 1989; Jones, 19991; Johnson, 1994], little work has been done on applying it to understand the actions of non-governmental organizations." If you only reference one author, then your readers may assume that only one author has published on this topic, or, conclude that you have not read the literature thoroughly knowing that others have published research in this area. Referencing multiple authors indicates to your readers a clear idea of the breadth of analysis you conducted about the research problem, not a distorted or incomplete one.
What if I find exactly what I want to say in the writing of another researcher? It depends on what it is; if someone else has investigated precisely the same research problem as you, then you likely will have to change your topic, or at the very least, find something new to say about what you're researching. However, if it is someone else's particularly succinct expression, but it fits perfectly with what you are trying to say, then you can quote directly, citing the page reference as well as the author and year of publication. Finding someone else who has stated or made the same point that you have is an opportunity to reinforce your own interpretation of the research problem.
How to Cite Other Sources in Your Paper. The Structure, Format, Content, and Style of a Journal-Style Scientific Paper. Department of Biology. Bates College; Lunsford, Andrea A. and Robert Connors; The St. Martin's Handbook. New York: St. Martin's Press, 1989; Research and Citation Resources. The Writing Lab and The OWL. Purdue University; Using Evidence. Writing Tutorial Services, Center for Innovative Teaching and Learning. Indiana University.
Most databases provide some kind of automatically generated citations for the major citation styles. Here is a video explaining how to find the citation feature in an EBSCO database: