[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