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Heinz College: 94-870 Telling Stories with Data: Citing Sources

This guide provides resources and guidance on how to properly use and cite images in your class projects.

Other Citation Style Resources

The Purdue Online Writing Lab including guides to APA, MLA and Chicago Styles


Citation guides by EasyBib for MLA, APA and Chicago styles

Practice Safe Writing!

Citing the works of authors that you use to form your own research is a critical part of the writing and research process. Citation provides evidence to back up our own ideas and statement. It demonstrates where our work fits into the greater body of knowledge.  And it gives proper credit where credit is due. 

Read these safe practices to avoid accidental plagiarism and check out these paraphrasing techniques.

CMU's University Policy on Academic Integrity

Get writing help from the Student Academic Success Center.



Zotero logo


Zotero is a popular free open source citation management tool that makes saving and citing online resources, including websites, YouTube videos, news articles, and scholarly database results, a breeze. Some of Zotero's strengths include its ability to capture a multitude of resource types with the click of a button, and its group library function, with no limit on group membership.  For more about Zotero, see this guide.

When to cite

When you create work for public consumption, whether it's a website, a journal article, a report or other type of publication, it is important to let your readers know when ideas, images, or phrases came from other sources.

In general, you should cite sources when you:

  • Use text, either quoted or paraphrased, from another source, even if it's a source that you previously authored.
  • Discuss an idea or concept based on another source, even if it's in your own words.
  • Use information you gathered from interviewing someone.
  • Use an image from another source, even if you modify the image in some way. (For more about citing images, see the How to Cite Images box)
  • Use data or statistics from another source, even if you create a new visualization from those data.

If you have any doubt about whether you should cite something, it's best to err on the side of caution and cite it. The only exception may be when something is common knowledge. Common knowledge includes folklore, common sense, and dates or well-known information about historical events. When in doubt, cite!

Remember, citing sources is good!  It demonstrates your knowledge of the literature and shows that you are building on existing research with new ideas and contributions.

How to cite

Citing a source requires two steps.

  • Step one: Place a citation at the end of the idea, paraphrase or direct quote in your text. Depending on the citation style you're using, this may be a superscripted number indicating a footnote or endnote, or the author's last name and year of publication in parentheses. On a website, you can also additionally include a hyperlink to the original source if it is another website or open digital resource.


  • Step two: Provide the full citation information at the end of your document or bottom of your website. This should include every piece of information that someone would need to find the original source that you used. Follow the citation style that you have chosen for your document and be consistent in using that style for all citations.

Testing your paraphrasing knowledge

Avoiding accidental plagiarism by properly paraphrasing, quoting and citing other resources is a critical skill for anyone producing content for the web. The following set of slides provides examples of incorrect and correct methods of using other sources. Press the Play button on the slide deck below and then advance the slides using the up and down arrow keys on your keyboard.