1. Homological Algebra;Cartan,1956
2. Cohomology of group extensions;Hochschild;Trans. Am. math. Soc.,1953
3. M. Shub: Endomorphisms of compact differentiable manifolds; to appear.
4. Differentiable dynamical systems;Smale;Bull. Am. math. Soc.,1967
5. R.F. Williams: One-dimensional non-wandering sets; to appear.