[1] Eklof P. C.: 
Set Theoretic Methods in Homological Algebra and Abelian Groups. Montreal University Press, Montreal 1980. 
MR 0565449 | 
Zbl 0488.03029[2] Osofsky B. L.: 
Homological Dimensions of Modules. Reg. Conf. Lecture Notes 12, Amer. Math. Soc, Providence 1973. 
MR 0447210 | 
Zbl 0254.13015[4] Trlifaj J.: 
Constructions and homological properties of simple von Neumann regular rings. to appear in Czech. Math. J. 40 (1990). 
MR 1084894 | 
Zbl 0741.16002[5] Trlifaj J.: 
Associative Rings and the Whitehead Property of Modules. Algebra-Berichte 63, R. Fischer Vlg., München 1990. 
MR 1053965 | 
Zbl 0697.16024