[1] BIRKHOFF G.: Extended arithmetic. Duke Math. J. 3 (1937), 312-316. MR 1545989 | Zbl 0016.38702

[2] BIRKHOFF G.: Generalized arithmetic. Duke Math. J. 9 (1942), 283-302. MR 0007031 | Zbl 0060.12609

[3] EILENBERG S.: Automata, Languages, and Machines. Volume B, Academic Press, New York 1976. MR 0530383 | Zbl 0359.94067

[4] JAKUBÍKOVÁ-STUDENOVSKÁ D.: On completions of partial monounary algebras. Czech. Math. J. 38 (113) 1988, 256-268. MR 0946294 | Zbl 0659.08003

[5] JÖNSSON B.: Topics in Universal Algebra. Lecture Notes in Mathematics 250, Springer Verlag, Berlin 1972. MR 0345895

[6] JÓNSSON B.: The arithmetic of ordered sets. In: Ordered sets (ed. I. Rival), 3-41, D. Reidel Publ. Comp., Dordrecht 1982. MR 0661290

[7] LOVÁSZ L.: Operations with structures. Acta Math. Acad. Sci. Hung. 18 (3-4), 1967, 321-328. MR 0214529 | Zbl 0174.01401

[8] MAC LANE S., BIRKHOFF G.: Algebra. Macmillan Comp., New York 1968.

[9] MARICA J. C., BRYANT S. J.: Unary algebras. Pacif. Math. J. 10 (1960), 1347-1359. MR 0118692 | Zbl 0163.26501

[10] MC KENZIE R. N., MC NULTY G. F., TAYLOR W. F.: Algebras, Lattices, Varieties. Volume I, Wadsworth&Brooks, Monterey, California 1987. MR 0883644

[11] NOVOTNÝ J.: Cardinal arithmetic of a certain class of monounary algebras. Čas. pro pӗst. mat. 111 (1986), 384-393. MR 0871714 | Zbl 0616.08012

[12] NOVOTNÝ J.: Morphisms of a certain class of monounary algebras. Math. Slovaca 38, 1988, 243-247. MR 0977901 | Zbl 0659.08004

[13] SKORNJAKOV L. A.: Unars. Collog. Math. Soc. János Bolyai 29, Univ. algebra, Esztergom 1977, 735-743. MR 0660907 | Zbl 0397.16042