[1] O. D. Artemovych, Minimal non-$PC$-groups, Algebra Discrete Math., 18 (2014) 1-7.
[2] V. V. Beljaev and N. F. Sesekin, Innite groups of Miller-Moreno type, Acta Math. Acad. Sci. Hungar., 26 (1975) 369-376.
[3] V. V. Beljaev, Minimal non-$FC$-groups, Sixth All-Union Symposium on Group Theory ( Cerkassy, 1978) (Russian), 221, "Naukova Dumka", Kiev, 1980 97-102.
[4] M. Bouchelaghem and N. Trab elsi, On minimal non- MrC -groups, Ric. Mat., 62 (2013) 97-105.
[5] N. S. Chernikov, A theorem on groups of nite special rank, Ukrainian Math. J., 42 (1990) 855-861.
[6] M. R. Dixon, M. J. Evans and H. Smith, Goups with all prop er subgroups nilpotent-by-nite rank, Arch. Math., 75 (2000) 81-91.
[7] M. De Falco, F. de Giovanni, C. Musella and N. Trabelsi, Groups whose proper subgroups of innite rank have nite conjugacy classes, Bul l. Aust. Math. Soc., 89 (2014) 41-48.
[8] F. de Giovanni, Innite groups with rank restrictions on subgroups, Problems in the theory of representations of algebras and groups, 3139, Part 25, Zap. Nauchn. Sem. POMI, 414, POMI, St. Petersburg (2013).
[9] F. de Giovanni and M. Tromb etti, Groups whose prop er subgroups of innite rank have polycyclic conjugacy classes, (to app ear).
[10] S. Franciosi, F. de Giovanni and M. J. Tomkinson, Groups with polycyclic-by-nite conjugacy classes, Boll. Un. Mat. Ital. B (7), 4 (1990) 35-55.
[11] L. A. Kurdachenko, On groups with minimax conjugacy classes, In: Innite groups and adjoining algebraic struc- tures, (Naukova Dumka, Kiev), 1999 160-177.
[12] L. A. Kurdachenko and J. Otal, Frattini properties of groups with minimax conjugacy classes, Topicsin Innite Groups, Topics in innite groups, Quad. Mat., 8, Dept. Math., Seconda Univ. Napoli, Caserta, 2001 221-237.
[13] J. Otal and J. M. Pe ~na, Minimal non- CC -groups, Comm. Algebra, 16 (1988) 1231-1242.
[14] D. J. S. Robinson, Finiteness conditions and generalized soluble groups, Springer Verlag, New York-Berlin, 1972.