1. Sugli omeomorfismi delle varieta`algebriche;Andreotti;Ann. Scuola Norm. Sup. Pisa,1969
2. Commutative Algebra;Bourbaki,1972
3. Prime ideals and integral dependence;Cohen;Bull. Amer. Math. Soc.,1946
4. On going down in polynomial rings;Dawson;Canad. J. Math.,1974
5. Direct limits and going-down;Dobbs;Comm. Math. Univ. Sancti Pauli,1982