http://www.cs.williams.edu/~kim/FOOPL/Bruce.1.2.gif ''Foundations of Object-Oriented Programming Languages'' by Kim B. Bruce (ISBN 0-262-02523-X). Good book on TypeTheory as applied to OO-languages. A bit simpler to digest than TypesAndProgrammingLanguages, though not as comprehensive of a treatment on the subject. ---- CategoryBook TypeTheory