unique indices...

Are there any other access methods in postgres 6.3.1 ,other than btree, to
create unique indices on relations with?


Thanks,
      
     __________________________________________________________________
     *  Lorenzo J. Huerta                                             *
     *  Programming Assistant                                         *
     *  Computing & Networking Networking Architecture and Operations *
     *  New Mexico State University                                   *
     *  phone: (w)(505)646-2582 (h)(505) 521-8699 fax:(505) 646-8139  *
     *  e-mail: lorenzo@nmsu.edu                                      *
     *  Web Site: http://web.nmsu.edu/~ljhuerta                       *
     __________________________________________________________________