1. Brualdi, R.A.: Introductory Combinatorics, 4th edn. Prentice Hall, Upper Saddle River (2004). 6 April 2004
2. Cameron, P.J.: Combinatorics: Topics, Techniques, Algorithms. Cambridge University Press, New York (2001)
3. Electronic Notes in Theoretical Computer Science;JJMM Rutten,2001
4. LNCS;JJMM Rutten,2004
5. Rutten, J.J.M.M.: Coinductive counting with weighted automata. J. Autom. Lang. Comb. 8(2), 319–352 (2003)