Are there any free implementations of Snobol4 available? Every couple of years I search for them again and I only find broken links...

(Btw, Icon - Snobol4's successor - was my favorite language for several years. When I tried to learn Snobol4 by myself in the university I couldn't understand its semantics, but the book "The Icon Programming Language" was superbly written and it explained generators and backtracking very well).