1. Abstraction and verification in Alphard: defining and specifying iteration and generators;Shaw;Commun. ACM,1977
2. Abstraction mechanisms in CLU;Liskov;Commun. ACM,1977
3. Reference Manual for the Icon Programming Language; Version 4;Coutant;University of Arizona Technical Report 81-4,1981
4. D. C. Smith and H. K. Enea. Backtracking in MLISP2, Proceedings of the 3rd International Joint Conference on Artificial Intelligence, pp. 677–685.
5. The design and implementation of a goal-directed programming language;Korb,1978