The most common copyright question the Copyright Committee gets can also be the hardest to answer. More than anything else we are asked "Is it okay for me to post this reading to my course shell?" and, for good and for ill, it is a question that is often without a clear answer. Fair use is the only copyright exception that would apply to this kind of use so it really comes down to doing a full and honest fair use analysis.
Some things that enhance a fair use argument:
Some things that weaken a fair use argument:
The Copyright Committee is glad to help talk you through your fair use evaluation of any given course reading.
Remember, too, that many articles and even book chapters can be accessed electronically using the library databases. Providing a permanent link to this licensed content allows you to avoid dealing with copyright issues altogether and, incidentally, might have the side effect of introducing your students to the wide world of library resources!