[comp.lang.prolog] Public domain Prolog for UNIX?

so@brownie.cs.wisc.edu (Bryan So) (11/06/90)

I have heard of a very good public domain Prolog originated from
Europe for UNIX.  I think the name is Sixtus or somewhere along 
the same pronunciation.

Has anybody heard of and had experience with it?  Where can I get
a copy?


Bryan So