1. J. L. Lions, Équations différentielles opérationnelles et problèmes aux limites, Springer 1961.
2. K. Yosida, Functional Analysis, Springer 1971 (Third Edition).
3. S. G. Krein, Linear differential equations in a Banach space, Izdat Nauka, Moscow 1967.
4. A. Friedman, Partial differential equations, Holt, Rinehart and Winston 1969.
5. R. W. Carroll, Abstract methods in partial differential equations, Harper and Row 1969.