1. Abadi, M., Cardelli, L., Curien, P.L., Lévy, J.-J.: Explicit substitutions. Journal of Functional Programming 4(1), 375–416 (1991)
2. The Alfa proof editor,
http://www.cs.chalmers.se/~hallgren/Alfa/
3. Ariola, Z., Felleisen, M., Maraist, J., Odersky, M., Wadler, P.: A call-by-need lambda calculus. In: Proceedings of the 22nd Symposium on Principles of Programming Languages, pp. 233–246. ACM Press, New York (1995)
4. Baader, F., Nipkow, T.: Term Rewriting and All That. Cambridge University Press, Cambridge (1998)
5. Studies in Logic and the Foundations of Mathematics;H. Barendregt,1984