1. J. Adamek, R. El Bashir, M. Sobral, J. Velebil, On functors which are lax epimorphisms, Theory Appl. Categories 8 (2001) 509–521 (http://www.tac.mta.ca/tac/).
2. Weak factorization systems and topological functors;Adamek;Appl. Categorical Struct.,2002
3. M.A. Bednarczyk, A.M. Borzyszkowski, W. Pawlowski, Generalized congruences—epimorphisms in Cat, Theory Appl. Categories 5 (1999) 266–280 (http://www.tac.mta.ca/tac/).
4. Sheafifiable homotopy model categories;Beke;Math. Proc. Cambridge Philos. Soc.,2000
5. A. Beligiannis, On the Freyd categories of an additive category, Homology Homotopy Appl. 2 (2000) 147–185 (http://www.rmi.acnet.ge/hha/).