1. N. S. Chemikov, “On the product of almost Abelian groups,” Ukr. Mat. Zh., 33, No. 1, 136–138 (1981).
2. N. S. Chemikov, Groups Factorizable into the Product of Permutable Subgroups [in Russian] Naukova Dumka, Kiev 1987.
3. B. Amberg, S. Franciosi, and F. De Giovanni, Products of Groups, Clarendon Press, Oxford 1992.
4. D. S. Kazarin, “On groups with factorization,” Dokl. Akad. Nauk SSSR, 256, No. 1, 26–29 (1981).
5. D. S. Kazarin, “On the product of two nilpotent groups,” in: Problems in Group Theory and Homologous Algebra [in Russian], Yaroslavl University, Yaroslavl (1981), pp. 62–66.