http://www.copyright.gov/title17/92chap1.html#107
Notwithstanding
the provisions of sections 106
and 106A, the
fair use of a copyrighted work, including such use by reproduction in copies or
phonorecords or by any other means specified by that
section, for purposes such as criticism, comment, news reporting, teaching
(including multiple copies for classroom use), scholarship, or research, is not
an infringement of copyright. In determining whether the use made of a work in
any particular case is a fair use the factors to be considered shall
include —
(1) the purpose and character of the use,
including whether such use is of a commercial nature or is for nonprofit
educational purposes;
(2) the nature of the copyrighted work;
(3) the amount and substantiality of the
portion used in relation to the copyrighted work as a whole; and
(4) the effect of the use upon the
potential market for or value of the copyrighted work.
The fact that a work is unpublished shall not itself bar a finding
of fair use if such finding is made upon consideration of all the above
factors.