[1] Z. HEDRLÍN A. PULTR:
On categorial embeddings of topological structures into algebraic. Comment. Math. Univ. Carolinae 7 (1966), 377-400.
MR 0202797
[2] A. PULTR:
On selecting of morphisms among all mappings between underlying sets of objects in concrete categories and realisation of these. Comment. Math. Univ. Carolinae 8 (1967), 53-83.
MR 0210764