1. On the order of doubly transitive permutation groups;Babai;Invent. Math.,1982
2. Permutation groups on unordered sets;Cameron,1977
3. Orbits of permutation groups on unordered sets;Cameron;J. London Math. Soc.,1978
4. Orbits of permutation groups on unordered sets, II;Cameron;J. London Math. Soc.,1981
5. P.J. Cameron, R.A. Liebler, Tactical decomposition and orbits of projective groups, to appear in Linear Algebra Appl.