1. Rational identities, and applications to algebra and geometry;Amitsur;J. Algebra,1966
2. Projective modules over free groups are free;Bass;J. Algebra,1964
3. Commuting elements in free algebras and related topics in ring theory;Bergman,1967
4. Modules over coproducts of rings;Bergman;Trans. Amer. Math. Soc.,1974
5. Coproducts and some universal ring constructions;Bergman;Trans. Amer. Math. Soc.,1974