Source : Free On-Line Dictionary of Computing

Prolog-II
     
        Prolog with two new predicates: "dif" for coroutines and
        "freeze" for delayed evaluation.
     
        Available from ExperIntelligence, Santa Barbara CA.
     
        ["Prolog II Reference Manual and Theoretical Model",
        A. Colmerauer, Internal Report, GroupeIA, U Aix-Marseille (Oct
        1982)].