1. Coherent functors;Auslander,1966
2. M. Auslander and M. Bridger: Stable module theory, (to appear).
3. Homological Algebra;Carton,1956
4. Homotopy idempotents;Freyd,1966
5. Natural maps of extension functors and a theorem of R.G. Swan;Hilton;Proc. Camb. Phil. Soc. math. phys. Sci.,1961