1. A. A. Albert, Structure of algebras, New York, 1939.
2. University of Michigan Publications in Mathematics, no. 1;Artin, Emil,1944
3. On the dimension of modules and algebras. III. Global dimension;Auslander, Maurice;Nagoya Math. J.,1955
4. W. C. Carter, On the cohomology theory of fields, unpublished doctoral dissertation, Harvard University, 1947.