This uses the Rail package, which allows you to include syntax
diagrams, also known as railroad diagrams, in a Latex document. Rail
is available for Internet anonymous FTP from host phiobos.cs.kun.nl in
the directory pub/Rail. If you cannot use FTP, mail copies can be
requested from L.W.J. Rooijakkers <lwj@cs.kun.nl>, University of
Nijmegen, The Netherlands.

I had to make one change to rail.sty, which is documented there.
