1. Graduate Texts in Mathematics;F.W. Anderson,1974
2. Bican, L.: Torsionfree precovers. In: Contributions to General Algebra, Proceedings of the Klagenfurt Conference 2003 (AAA 66), vol. 15. Verlag Johannes Heyn, Klagenfurt (2004)
3. Bican, L., El Bashir, R., Enochs, E.: All modules have flat covers. Proc. Lond. Math. Soc. 33, 649–652 (2001)
4. Bican, L., Kepka, T., Němec, P. Rings, Modules, and Preradicals. Marcel Dekker, New York (1982)
5. Bican, L., Torrecillas, B.: Precovers. Czech. Math. J. 53(128), 191–203 (2003)