1. On projective modules over semihereditary rings;Albrecht,1961
2. Projective modules over free groups are free;Bass;J. Algebra,1964
3. Hereditarily and cohereditarily projective modules;Bergman,1972
4. Morita Equivalence and Duality;Cohn,1966
5. Rings with a transfinite weak algorithm;Cohn;Bull. London Math. Soc.,1969