1. Extremal Graph Theory;Bollobás,1978
2. Problèmes combinatoires de commutation et rèarrangements;Cartier,1969
3. Graphs and Digraphs;Chartand,1986
4. The number of words of length n in a free “semi-abelian” monoid;Fisher;Amer. Math. Monthly,1989
5. D.C. Fisher, The number of triangles in a K4-free graph, to appear in Discrete Mathematics.