Notwithstanding the provisions of section 106, 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.