[[1] Carathéodory, Constantin. Vorlesungen über reelle Funktionen. Leipzig, Berlin: Vieweg, Teubner Verlag, 1927. Cited on 118.10.1007/978-3-663-15768-7]Search in Google Scholar
[[2] Kuratowski, Casimir. Topologie. Vol. I. Warszawa: Polskie Towarzystwo Matematyczne, 1952. Cited on 119.]Search in Google Scholar
[[3] Sibirskiĭ, Konstantin S. Introduction to topological dynamics. Leiden: Noordhoff International Publishing, 1975. Cited on 117.10.1007/978-94-010-2308-5_1]Search in Google Scholar