There are two basic and universal rules regarding the use of information in academic writing:

1. If you use the language of your source, you must quote it exactly, enclose it in quotation marks, and cite the source. If you use the language of your source, quote the wording exactly. This is called a direct quotation. A direct quotation is either enclosed in quotation marks or indented on the page. If you omit part of the wording, use an ellipsis (three periods, four if necessary for punctuation to indicate the omission). In any case, several words in succession taken from another source constitute direct quotation and must be acknowledged.

A paraphrase employs source material by restating an idea in an entirely new form that is original in both sentence structure and word choice. Taking the basic structure from a source and substituting a few words is an unacceptable paraphrase and may be construed as plagiarism. Creating a new sentence by merging the wording of two or more sources is also plagiarism. The penalty for plagiarism is an automatic Fail for this class and a letter of notification to the Committee on Discipline.

1. If you use ideas or information that are not common knowledge, you must cite a source.

fonte:http://ocw.mit.edu/OcwWeb/Writing-and-Humanistic-Studies/21W-732-2Intro-to-Tech-CommunicationFall2002/Syllabus/index.htm