1. Subtyping recursive types;Amadio;ACM Trans. Programming Lang. Systems,1993
2. On subtyping and matching;Abadi;ACM Trans. Programming Lang. Systems,1996
3. A Theory of Objects;Abadi,1986
4. A fixed point extension of the second order lambda calculus: observational equivalences and models;Amadio,1988
5. Recursion over realizability structures;Amadio;Inform. and Comput.,1991