On extensions onto sub-semigroups of semigroups with two generators. Z. Hedrlin; J. Kastl — 1971 Semigroup forum
Relations (Graphs) with Given Finitely Generated Semigroups. Z. Hedrlin; A. Pultr — 1964 Monatshefte für Mathematik
Relations (Graphs) with Given Infinite Semigroups. Z. Hedrlin; A. Pultr — 1964 Monatshefte für Mathematik
Symmetric Relations (Undirected Graphs) with Given Semigroups. Z. Hedrlin; A. Pultr — 1965 Monatshefte für Mathematik
On subsemigroups of transformation semigroups with two generators. Z. Hedrlin; P. Goralcik — 1970 Semigroup forum
A game of composing binary relations P. GoralČík; Z. Hedrlín; V. Koubek; J. Ryšunková — 1982 RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications
Concerning a categorial approach to topological and algebraic theories Hedrlín, Z.; Pultr, A.; Trnková, V. — 1967 General Topology and its Relations to Modern Analysis and Algebra