1. R. Bieri, Homological Dimension of Discrete Groups, 2nd ed. QMW College Math. Notes. in: Queen Mary College, Department of Pure Mathematics, London, 1981
2. Deficiency and the geometric invariants of a group;Bieri;J. Pure Appl. Algebra,2007
3. R. Bieri, R. Strebel, Invariants for Discrete Groups, manuscript-book, Frankfurt University
4. Valuations on free resolutions and higher geometric invariants of groups;Bieri;Comment. Math. Helv.,1988
5. Cohomology of Groups;Brown,1994