[1] Bartol W.: On the existence of machine homomorphisms I. Bull. Acad. Polon. Sci., Sér. Sci. Math. Astr. Phys. 19 (1971), 856-869; II, ibid., 20 (1972), 773-777. MR 0314574

[2] Bartol W.: Algebraic complexity of machines. Bull. Acad. Polon. Sci., Sér. Sci. Math. Astr. Phys. 22 (1974), 851-856. MR 0356577 | Zbl 0298.68041

[3] Bartol W.: Dynamics programs of computations. (Polish), Warszawa 1974.

[4] Jónsson В.: Topics in universal algebra. Berlin 1972.

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

[6] Kopeček O.: Construction of all machine homomorphisms. Bull. Acad. Polon. Sci., Sér. Sci. Math. Astr. Phys. 8 (1976), 655-658. MR 0431792

[7] Kopeček O.: The category of connected partial unary algebras. Czech. Math. J. 27 (102) (1977), 415-423. MR 0453612

[8] Kopeček O.: Homomorphisms of machines I. Arch. Math. (Brno) 1 (1978), 45 - 50; II, ibid., 2(1978), 99-108. MR 0512743

[9] Kopeček O.: Existence of monomorphisms of partial unary algebras. Czech. Math. J. 28 (103) (1978), 462-473. MR 0485638

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

[11] Novotný M.: On a problem from the theory of mappings. (Czech), Publ. Fac. Sci. Univ. Masaryk, No 344 (1953), 53-64.

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

[13] Novotný M.: Construction of all homomorphisms of unary algebras. (Czech), Dept. Math. Ped. Fac. Univ. J. E. Purkyně, Seminar on new directions in mathematical education, Brno, 1973.