[1] P. Burmeister, B. Wojdylo: Properties of homomorphisms and quomorphisms between partial algebras. Contributions to general algebra 5, Proc. of Salzburg Conference (1986), 69–90. MR 0930911

[2] D. Jakubíková-Studenovská: Systems of unary algebras with common endomorphisms I, II. Czech. Math. J. 29 (104) (1979), 406–420, 421–429. MR 0536068

[3] D. Jakubíková-Studenovská: Endomorphisms and connected components of partial monounary algebras. Czech. Math. J. 35 (110) (1985), 467–489. MR 0803041

[4] D. Jakubíková-Studenovská: Endomorphisms of partial monounary algebras. Czech. Math. J. 36 (111) (1986), 467–489. MR 0847767

[5] O. Kopeček: Homomorphisms of partial unary algebras. Czech. Math. J. 26 (101) (1976), 108–127. MR 0392759

[6] O. Kopeček, M. Novotný: On some invariants of unary algebras. Czech. Math. J. 24 (99) (1974), 219–246. MR 0347703

[7] E. Nelson: Homomorphisms of monounary algebras. Pacif. J. Math. 99 (1982 (2)), 427–429. DOI 10.2140/pjm.1982.99.427 | MR 0658072

[8] M. Novotný: Sur un probleme de la theorie des applications. Publ. Fac. Sci. Univ. Masaryk 344 (1953), 53–64. MR 0061149

[9] M. Novotný: Über Abbildungen von Mengen. Pacif. J. Math. 13 (1963), 1359–1369. DOI 10.2140/pjm.1963.13.1359 | MR 0157143