1. On index and normal solvability of general elliptic boundary value problems with finite group of shifts;Antonevich;Differentsial'nye Uravneniya,1972
2. On some simple generalizations of linear elliptic boundary value problems;Bitsadze;Dokl. Akad. Nauk SSSR,1969
3. Non-local elliptic boundary value problems;Browder;Amer. J. Math.,1964
4. Linear Operators;Dunford,1963
5. On the boundary value problems for strongly elliptic systems;Guseva;Dokl. Akad. Nauk SSSR,1955