1. Filter models and easy terms;Alessi,2001
2. Simple easy terms;Alessi,2002
3. Omega can be anything it should not be;Baeten;Proc. K. Ned. Akad. Wet., Ser. A, Indag. Math.,1979
4. Some extensional term models for lambda calculi and combinatory logics;Barendregt,1971
5. The Lambda-Calculus, Its Syntax and Semantics;Barendregt,1984