1. V. A. Vedernikov, “Tests for solvability and supersolvability of finite groups,” Sibirsk. Mat. Zh. 8, 1236–1244 (1967) [in Russian].
2. P. I. Trofimov, “Non-simplicity and solvability criteria for finite groups,” Sibirsk. Mat. Zh. 3, 876–881 (1962).
3. D. C. Buchthal, “On factorized groups,” Trans. Amer. Math. Soc. 183, 423–430 (1973).
4. J. Zhang, “Sylow numbers of finite groups,” J. Algebra 176(1), 111–123 (1995).
5. Guo Wenbin, “Finite groups with given indices of normalizers of Sylow subgroups,” Sibirsk. Mat. Zh. 37(2), 295–300 (1996) [Siberian Math. J. 37 (2), 253–257 (1996)].