1. Interactive Theorem Proving and Program Development: Coq'Art: The Calculus of Inductive Constructions;Bertot,2004
2. Five axioms of alpha-conversion;Gordon,1996
3. McBride, C. and J. McKinna, Functional pearl: I am not a number—I am a free variable, in: Haskell '04: Proceedings of the 2004 ACM SIGPLAN Workshop on Haskell (2004), pp. 1–9