[1] Z. HEDRLÍN: 
Extensions of structures and full embeddings of categories. Actes du Congrès Internat. des Mathématiciens 1970, tome 1, Paris 1971, 319-322. 
MR 0419554[2] Z. HEDRLÍN J. LAMBECK: 
How comprehensive is the category of semigroups?. J. Algebra 11 (1969), 195-212. 
MR 0237611[3] Z. HEDRLÍN A. PULTR: 
On representation of small categories. (in Russian), Dokl. Akad. Nauk SSSR 160 (1965), 284-286. 
MR 0172908[4] Z. HEDRLÍN A. PULTR: 
On full embeddings of categories of algebras. Illinois J. of Math. 10 (1966), 392-406. 
MR 0191858[5] Z. HEDRLÍN A. PULTR: 
On categorial embeddings of topological structures into algebraic. Comment. Math. Univ. Carolinae 7 (1966), 377-400. 
MR 0202797[6] L.  KUČERA: Full embeddings  of categories. (in Czech), CSc. Thesis, Charles University, 1974.
[7] L. KUČERA A. PULTR: 
Non-algebraic concrete categories. J. Pure and Appl. Alg. 3 (1973), 95-102. 
MR 0335594[8] A. PULTR V. TRNKOVÁ: Combinatorial, Algebraic and Topological Categories. Academia, Prague, 1980.
[9] P. VOPĚNKA Z. HEDRLÍN A. PULTR: 
A rigid relation exists on any set. Comment. Math. Univ. Carolinae 6 (1965), 149-155. 
MR 0183647