Richard Bonichon David Delahaye Damien Doligez Zenon : An Extensible Automated Theorem Prover Producing Checkable Proofs. 151-165 2007 conf/lpar/2007 LPAR http://dx.doi.org/10.1007/978-3-540-75560-9_13 db/conf/lpar/lpar2007.html#BonichonDD07