1. Aiello, L., Aiello, M. and Weyhrauch, R.W., "The Semantics of PASCAL in LCF", Artificial Intelligence Memo No. 221 Stanford University (1973).
2. Dijkstra, E.W., "Notes on Structured Programming", Structured Programming, by Dahl, O.J., Dijkstra, E.W. and Hoare, C.A.R., Academic Press, 1–82 (1972).
3. Hoare, C.A.R. and Wirth, N. "An Axiomatic Definition of the Programming Language PASCAL", Eidg. Technische Hochschule, Zurich, Berichte der Fachgr, Computer-Wissenschaften, Nr. 6 (1972) also in Acta Informatica 2, 335–355 (1973).
4. Igarashi, S., London, R.L. and Luckham D.C., "Automatic Program Verification I: A Logical Basis and its Implementation", Artificial Intelligence Memo No. 200, Stanford University (1973).
5. Knuth, D., "The Art of Computer Programming", Addison Wesley Pub. Comp. (1968).