If you use data from secondary sources, the data must be documented; that is, you must indicate where the data originated. Using the ideas of someone else without giving credit is plagiarism and is unethical.

Even if you paraphrase and put the information in your own words, the ideas must be documented. In citing sources, you should use direct quotations sparingly. Good writers use the exact words of another writer to emphasize opinions because of the author's status as an expert; duplicate the exact wording before criticizing; or repeat identical phrasing because of its precision, clarity, or aptness.

Citing sources strengthens your argument as a writer, and shields you from charges of plagiarism.