1. R. A. Adams,Sobolev Spaces, Academic Press, New York, 1975.
2. V. Barbu,Nonlinear Semigroups and Differential Equations in Banach Spaces, Noordhoff International Publishing, Leyden, The Netherlands, 1976.
3. V. Barbu,A semigroup approach to an infinite delay equation in Hilbert Space, inAbstract Cauchy Problems and Functional Differential Equations (F. Kappel and W. Schappacher, eds.), Pitman Publishing Inc., Boston, 1981, pp. 1–25.
4. H. Brezis and A. Pazy,Convergence and approximation of semigroups of nonlinear operators in Banach spaces, J. Funct. Anal.9 (1972), 63–74.
5. Lecture Notes in Math;G. Chen,1978