Prolog - Tutorials

http://www.swi-prolog.org/

 http://www.gprolog.org/

http://en.wikibooks.org/wiki/Prolog

http://www.doc.gold.ac.uk/~mas02gw/prolog_tutorial/prologpages/

https://www.csupomona.edu/~jrfisher/www/prolog_tutorial/intro.html