1. B. Bollobás, P. Erd?s, M. Simonovits, andE. Szemerédi: Extramal graphs without large forbidden subgraphs, Advances in Graph Theory, B. Bollobás ed.,Annals of Discrete Mathematics,3 (1978), 29?41, also appeared as a problem inB. Bollobás:Extremal Graph Theory, Academic Press 1978, p. 367 Problem 47.
2. R. Häggkvist: Odd cycles of specified length in non-bipartite graphs,Graph Theory, B. Bollobás ed.,Annals of Discrete Mathematics,13 (1982), 89?100.
3. A. Lubotzky, R. Phillips, P. Sarnak: Ramanujan graphs,Combinatorica,8 (1988), 261?277.