1. Arkhangelskii, A. and Ponomarev, V.: The Principles of General Topology through Problems and Exercises, Moscow: Nauka 1974
2. Balanov, Z.: On finite coverings of ann-dimensional sphere and Ljusternik Theorem. Topological structures and its mappings, Riga: Riga Univ., 27–33 (1987) [Russian]
3. Balanov, Z.: Geometric methods in a theory of equivariant vector fields. Riga: Riga Polytechn. Inst. Press, 1988 [Russian]
4. Balanov, Z.: A comparison principle for equivariant mappings in non-linear analytical problems. Dissertation. Minsk: Belorussian University 1989 [Russian]
5. Balanov, Z. and Brodsky S.: Comparison principle of Krasnoselski and extension of equivariant maps. Functional Analysis. Operator Theory. Ul'yanovsk: Ul.gos.ped.inst.23, 18–31 (1984) [Russian]