Here are links (URLs) to copyright information at Wikipedia.

Robbie Rhodes - MMDigest

http://en.wikipedia.org/wiki/Copyright_Term_Extension_Act 
  The Copyright Term Extension Act.  This law, also known as the Sonny
Bono Copyright Term Extension Act, Sonny Bono Act, or as the Mickey
Mouse Protection Act ...  The Walt Disney Company lobbied extensively
on behalf of the Act, which delayed the entry into the public domain of
the earliest Mickey Mouse movies, leading to the nickname "The Mickey
Mouse Protection Act".  In addition to Disney, California congresswoman
Mary Bono (Sonny Bono's widow and Congressional successor), and the
estate of composer George Gershwin supported the act.

http://en.wikipedia.org/wiki/United_States_copyright_law#Major_Amendments_to_U.S._Copyright_Law 
  Since 1790, Congress has amended US Copyright law several times.
Major amendments include ...

http://en.wikipedia.org/wiki/United_States_copyright_law#Pre-1976_Dual_State_and_Federal_Copyright_law 
  Before the 1976 Copyright Act, copyright protection was provided by
a dual system under both federal and state laws. ...

http://en.wikipedia.org/wiki/Berne_Convention_for_the_Protection_of_Literary_and_Artistic_Works 
  ... an international agreement governing copyright, which was first
accepted in Berne, Switzerland, in 1886 ... developed at the instigation
of Victor Hugo ...

http://en.wikipedia.org/wiki/Orphan_works 
  An orphan work is a copyrighted work for which the copyright owner
cannot be contacted. ... Orphan works are not available for use by
filmmakers, archivists, writers, musicians, and broadcasters.

http://en.wikipedia.org/wiki/Public_domain 
  This article is about public ownership of creative works.