1. M. F.Atiyah and I. G.MacDonald, Introduction to Commutative Algebra. Massachusetts 1969.
2. R.Bieri, Homological Dimension of Discrete Groups. Queen Mary College Mathematics Notes, 1976.
3. K. S.Brown, Cohomology of Groups. Graduate Texts in Mathematics87, Berlin-New York 1982.
4. K. W. Gruenberg, Relation Modules of Finite Groups. CBMS no.25, Amer. Math. Soc., Providence, R. I. 1976.
5. T. Y.Lam, Serre's Conjecture. LNM635, Berlin-New York 1978.