1. Abbas, A., Programming with types and rules in Martin-Lof's theory of types, Ph.D. thesis, London University, 1987
2. Backhouse, R., Overcoming the mismatch between programs and proofs, Proc. workshop on programming logic, pp 116–122, Marstrand, June 1987.
3. Backhouse, R., et al, Do-it-yourself type theory, tech. rep. CS 8811, Dept. Maths. and computing science, University of Gronigen, 1988; to appear: Formal aspects of computing, 1989.
4. Beeson, M. J., Foundations of constructive mathematics, Springer Verlag, 1985
5. Beeson, M. J., Proving programs and programming proofs, Logic, Methodology and Philosophy of Science VII, North Holland, pp 51–82, 1986