[1] Bar-Hillel, Y., Fraenkel, A. A., and Lévy, A.: Foundations of Set Theory. North Holand, Amsterdam, 1973.
[2] Bourbaki, N.: 
Topologie générale. Eléments de Mathématique, I. part., livre III, Paris, 1940. 
Zbl 0026.43101[3] Čech, E.: Topological spaces. Topological papers of Eduard Čech, Academia, Prague, 1968.
[4] Čech, E.: 
Topological Spaces (Revised by Z. Frolík and M. Katětov). Academia, Prague, 1966. 
MR 0211373[5] Mac Lane, S.: 
Categories for the Working Mathematician. Springer-Verlag, New York-Heidelberg-Berlin, 1971. 
MR 0354798 | 
Zbl 0232.18001[6] Novák, V., and Novotný, M.: 
Transitive ternary relations and quasiorderings. Arch. Math. Brno 25 (1989), 5–12. 
MR 1189193[7] Novotný, M.: 
Ternary structures and grupoids. Czech. Math. J. 41 (1991), 90–98. 
MR 1087627[8] Šlapal, J.: 
On closure operations induced by binary relations. Rev. Roum. Math. Pures et Appl. 33 (1988), 623–630. 
MR 0962612[9] Šlapal, J.: 
Relations of type $ $Zeitschr. für Math. Logik und Grundl. der Math. 34 1988 563–573.  
MR 0973399