Citing Sources: Fair Use

"Fair Use:  A provision for fair use is found in the Copyright Act at Section 107. Under the fair use provision, a reproduction of someone else's copyright-protected work is likely to be considered fair if it is for limited use for one of the following purposes: criticism, comment, news reporting, teaching, scholarship and research. If the reproduction is for one of these purposes, a determination as to whether the reproduction is fair use must be made based upon four factors:
1. The purpose and character of use (principally, whether for commercial or nonprofit educational use);
2. The nature of the copyright-protected work (is the work published, unpublished or not released to the public domain, unpublished and non-public works have very limited Fair Use);
3. The amount and substantiality of the portion used (limited/short passages and material not “central” to the work are typically Fair Use); and
4. The effect of the use being evaluated upon the potential market for or value of the copyright-protected work. (i.e. If the work can be purchased or obtained commercially, it is typically NOT considered Fair Use.) 

Additionally, repeated use over several terms or courses weighs against fair use, particularly if any of the other criteria are not met. If your use does not meet the above criteria and the work is protected by copyright, you probably need to obtain permission to use the work from the copyright holder or its agent. When in doubt, obtain permission. "