Robbert Krebbers, Freek Wiedijk. A Formalization of the C99 Standard in HOL, Isabelle and Coq. In James H. Davenport, William M. Farmer, Josef Urban, Florian Rabe, editors, Intelligent Computer Mathematics - 18th Symposium, Calculemus 2011, and 10th International Conference, MKM 2011, Bertinoro, Italy, July 18-23, 2011. Proceedings. Volume 6824 of Lecture Notes in Computer Science, pages 301-303, Springer, 2011. [doi]