1. Abstract Galois theory;Barr;J. Pure Appl. Algebra,1980
2. Abstract Galois theory, II;Barr;J. Pure Appl. Algebra,1982
3. On locally simply connected toposes and their fundamental groups;Barr;Cahiers Topologie Géom. Différentielle Catégoriques,1981
4. Galois theory and cohomology of commutative rings;Chase;Mem. Amer. Math. Soc.,1965
5. Hopf algebras and Galois theory;Chase,1969