1. O. Yu. Schmidt, “Groups all subgroups of which are special,” Mat. Sb., 31, 366–372 (1924).
2. N. F. Kuzennyi and S. S. Levishchenko, "Finite Schmidt's groups and their generalizations," Ukr. Mat. Zh., 43, No. 7-8, 963-968 (1991)
3. English translation: Ukr. Math. J., 43, No. 7-8, 904-908 (1991).
4. V. S. Monakhov, “Schmidt subgroups, their existence, and some applications,” in: Proceedings of the Ukrainian Mathematical Congress, Institute of Mathematics, Ukrainian National Academy of Sciences, Kiev, No. 1 (2002), pp. 81–90.
5. V. N. Knyagina and V. S. Monakhov, “On finite groups with some subnormal Schmidt subgroups,” Sib. Mat. Zh., 45, No. 6, 1316–1322 (2004).