Copyright (c) 2006, William Stein

I make these notes available under the GNU Free Documentation License,
which allows for free redistribution, modification, etc. 

    The purpose of this License is to make a manual, textbook, or
    other functional and useful document "free" in the sense of
    freedom: to assure everyone the effective freedom to copy and
    redistribute it, with or without modifying it, either commercially
    or noncommercially. Secondarily, this License preserves for the
    author and publisher a way to get credit for their work, while not
    being considered responsible for modifications made by others.

See for complete details.