1. Pontryagin, L.S. Continuous groups (Nauka, Moscow, 1984) [in Russian].
2. Grigorian, S.A., Gumerov, R.N., Kazantsev, A.V. “Group structure in finite coverings of compact solenoidal groups”, Lobachevskii J. Math. 6, 39–46 (2000).
3. Clark, A. “A generalization of Hagopian’s theorem and exponents”, Topol. Appl. 117 (3), 273–283 (2002).
4. Grigorian, S.A., Gumerov, R.N. “On a covering group theorem and its applications”, Lobachevskii J. Math. 10, 9–16 (2002).
5. Bogatyi, S.A., Frolkina, O.D. “Classification of generalized solenoids” (in: Tr. sem. on vector and tensor analysis with their appl. to geom., mech. and phys. XXVI, pp. 31–59 (Izd-vo MGU, Moscow, 2005)) [in Russian].