1. V. M. Busarkin and Yu. M. Gorchakov, Finite Decomposable Groups [in Russian], Nauka (1968).
2. V. M. Busarkin and B. K. Durakov, "A class of finite unsolvable groups," Algebra i Logika,13, No. 2, 153?167 (1974).
3. V. V. Kabanov, "Finite groups with a self-centralizing subgroup of order 6 and one class of involutions," Algebra i Logika,11, No. 5, 516?534 (1972).
4. V. D. Mazurov, "Centralizers of involutions in simple groups," Matem. Sborn.,93, No. 4, 530?540 (1974).
5. G. Higman, Odd Characterization of Finite Simple Groups, Univ. Michigan (1968).