1. Artemov S.N., Silver B.: Arithmetically complete modal theories. Six papers in logic (AMS translations). Am. Math. Soc. 2, 39–54 (1987)
2. Bender E.A., Williamson S.G.: Foundations of Combinatorics with Applications. Dover, New York (2006)
3. Bou F., Joosten J.J.: The closed fragment of IL is PSPACE hard. Electron. Notes in Theor. Comput. Sci. 278, 47–54 (2011)
4. Čačić, V., Vuković, M.: A note on normal forms for the closed fragment of system IL. Math. Commun. 17, 195–204 (2012), also available at http://hrcak.srce.hr/file/123527
5. Flajolet P., Odlyzko A.: Singularity analysis of generating functions. SIAM J. Discrete Math. 3, 216–240 (1990)