You should cite in order to both provide credit where it's due, and also to allow those reading your work to find the same original source material. The Purdue OWL has a helpful guide here. Columbia College's guide to citing sources is also useful.

You must cite all sources that have directly or indirectly contributed to your analysis, synthesis, and/or argument in the work you submit.


You should quote your sources when it is important to convey the original author’s precise words.

  • If you use the exact text – words, phrases, sentences – you must enclose them in quotation marks and cite.
  • Short quotes – words and phrases – can be embedded into the text you write. Longer quotes – sentences and paragraphs – should be indented and separated from your words.


  • If you rewrite the original text in your own words, you must cite the source.


  • If you summarize the argument or data of another author, you must cite the source.


  • You must cite any text you read that helped you think about your paper even if you do not reference it directly in the text of your paper.
  • If a person assisted you in clarifying your thoughts – either in conversation or email correspondence – you must cite this source.

One way might be to acknowledge in a footnote connected to your paper’s title or opening sentence your indebtedness to a book or person (noting the date(s) of any relevant conversation or correspondence). Alternatively, for a more significant piece of work – such as an independent study or senior thesis – you can include a paragraph of acknowledgements, noting the range of assistance you received from many people.

Common Knowledge

Common knowledge is information that a reader can reasonably be expected to know. It does not need to be cited.

  • For example, “Barack Obama, the 44th President of the United States, was a student of Columbia College” can be considered to be common knowledge and does not need to be referenced.

However, common knowledge does not include opinion.

  • For example, you might agree with the statement “Columbia College is the best college” – but this is an opinion, not common knowledge and to make this case you would have to cite sources and data that support the supposition.

You should therefore be careful in the assumptions that you make in assessing what might be considered common knowledge.

Moreover, what might be common knowledge in one discipline might not be common knowledge in another discipline. It is important, then, to learn from your instructor the expectations for citing common knowledge in any given class.

If in any doubt, err on the side of caution and cite your source.