1. Miklos Ajtai. The complexity of the pigeonhole principle. In Proceedings of the 29th Annual IEEE Symposium on Foundations of Computer Science, pages 346–355, 1988.
2. Miklos Ajtai. The independence of the modulo p counting principles. In Proc. 26th ACM Symp. on Theory of Computing,pages 402–411, 1994.
3. Mathias Baaz and Pavel Pudlák. Kreisel’s conjecture for Lat. In Peter Clote and Jan Krajícek, editors, Arithmetic Proof Theory and Computational Complexity, pages 30–39. Oxford Univ. Press, 1993.
4. Paul Beame, Russell Impagliazzo, Jan Krajícek, Toniann Pitassi, Pavel Pudlák, and Alan Woods. Exponential lower bounds for the pigeonhole principle. In Proceedings of the 24th Annual ACM Symposium on Theory of Computing, pages 200–221, 1992.
5. A. Bezboruah and J. Shepherdson. Gödel’s second incompleteness theorem for Q. J. Symbolic Logic, pages 503–512, 1976.