[1] G. Birkhoff: Lattice Theory. rev. ed., Princeton University Press, New York, 1948. MR 0029876 | Zbl 0033.10103

[2] N. Bourbaki: Topologie générale, chap. I. (2nd ed.), Act. Sci. et. Ind., Paris, 1951.

[3] О. Hájek: Dynamical Systems in the Plane. Academic Press.

[4] A. Г. Курош: Теория групп. Гостехиздат, Москва, 1953. Zbl 1151.94459

[I] О. Hájek: Theory of processes I. Czech. Math. Journal 17 (92), (1967), 159- 199. MR 0212311