[1] L. BUKOVSKÝ Z. HEDRLÍN A. PULTR: On topological representation of semigroups and small categories. to appear in Matematicko-fyzikálny časopis SAV. MR 0191933

[2] Z. HEDRLÍN A. PULTR: Remark on topological spaces with given semigroups. Comm. Math. Univ. Car. 4, 4, 161-163 (1963). MR 0166768

[3] Z. HEDRLÍN A. PULTR: Symmetric relations (Undirected graphs) with given semigroups. to appear in Mh. Mathematik. MR 0188082

[4] A. PULTR Z. HEDRLÍN: Relations (Graphs) with given infinite semigroups. Mh. Mathematik 58, 421-425 (1964). . MR 0170841

[5] A. PULTR: Concerning universal categories. Comm. Math. Univ. Car. 5, 4, 227-239 (1964). MR 0173696 | Zbl 0135.02101

[6] A. ПУЛЬТР З. ГЕДРЛИН: О представлении малых категорий. to appear in Докл. Акад. Наук CCCP.