Adding book about Prolog CLP programming (English and Polish)

Free book about programming techniques in Prolog pubilshed in two languages:

"A Gentle Guide to Constraint Logic Programming via ECLiPSe"
http://anclp.pl/

"Programowanie w logice z ograniczeniami: Łagodne wprowadzenie dla platformy ECLiPSe"
http://www.pwlzo.pl/