From UofL's Student Handbook, Code of Student Rights and Responsibilities, Section 5E
Representing the words or ideas of someone else as one’s own in any academic exercise, such as:
1. Submitting as one’s own a paper written by another person or by a commercial “ghost writing” service,
2. Exactly reproducing someone else’s words without identifying the words with quotation marks or by appropriate indentation, or without properly citing the quotation in a footnote or reference.
3. Paraphrasing or summarizing someone else’s work without acknowledging the source with a footnote or reference.
4. Using facts, data, graphs, charts, or other information without acknowledging the source with a footnote or reference. Borrowed facts or information obtained in one’s research or reading must be acknowledged unless they are “common knowledge”. Clear examples of “common knowledge” include the names of leaders of prominent nations, basic scientific laws, and the meaning of fundamental concepts and principles in a discipline. The specific audience for which a paper is written may determine what can be viewed as “Common knowledge”: for example, the facts commonly known by a group of chemists will differ radically from those known by a more general audience.
Students should check with their teachers regarding what can be viewed as “common knowledge” within a specific field or assignment, but often the student will have to make the final judgment.
When in doubt, footnotes or references should be used.