"normal.opn" and "normal.pgn" are "sjeng"-compatible chess data files.
These files were obtained originally from:

      http://www.opensource.apple.com/darwinsource/Current/\
Chess-103.0.3/sjeng/books/normal.opn

      http://www.opensource.apple.com/darwinsource/Current/\
Chess-103.0.3/sjeng/books/normal.pgn

Note:  These URLs were valid as of early 2007.  However, they may have
broken since then.
