1. W. Arendt Vector-valued Laplace transforms and Cauchy problems Israel J. Math 59 (1987), 327–352.
2. W. Arendt and H. Kellerman Integrated solutions of Volterra integrodifferential equations and applications Volterra Integrodifferential Equations in Banach Spaces, Pitman Res. Notes in Math. vol. 190, 1989, pp. 21–51.
3. H. Berens, Interpolationsmethoden sur Behandlung von Approximationsprozessen auf Banachraumen, Lect. Notes Math. 64. Springer-Verlag, Berlin-Heidel-bergNew York, 1968
4. P.L. Butzer and H. Berens Semi-Groups of Operators and Approximation Springer-Verlag, New York, 1967
5. P. L. Butzer and A. Gessinger Ergodic theorems for semigroups and cosine operator functions at zero and infinity with rates; applications to partial differential equation: A survey Contemp. Math. 190 (1995), 67–94.