1. Geographical Encyclopedic Dictionary, Concepts and Terms. A.F. Treshnikov, Moscow, Russia (1988)
2. Sharygin, M.D.: Socio-economic regions: problems of cognition and organization. Selected Works, pp. 276–280. Publishing House of Perm State University, Perm, Russia (2010)
3. Animitsa, E.G., Sharygin, M.D.: The phenomenon of the territorial border. Geogr. Bull. 1–2, 5–10 (2007)
4. Shuvalov, V.E.: To the concept of geographical border. Materials of the III All-Union Seminar on theoretical issues of geography. Kyiv (1977)
5. Rodoman, B.B.: Territorial Reales and Networks. Smolensk, Russia (1999)