1. Introduction to Commutative Algebra;Atiyah,1969
2. Free Rings and their Relations;Cohn,1971
3. Automorphisms of free algebras of rank two, I;Czerniakiewicz;Trans. Amer. Math. Soc.,1971
4. Automorphisms of free algebras of rank two, II;Czerniakiewicz;Trans. Amer. Math. Soc.,1972
5. The structure of the automorphism group of polynomial rings;Fraser;J. Algebra,1973