1. W. Arendt, P. R. Chernoff andT. Kato, A generalization of dissipativity and positive semigroups. J. Operator Theory8, 167?180 (1982).
2. E. B.Davies, One-Parameter Semigroups. London 1980.
3. C. Kipnis, Majoration des semi-groupes de contractions deL 1 et applications. Ann. Inst. H. Poincaré10, 369?384 (1974).
4. Y. Kubokawa, Ergodic theorems for contraction semigroups. J. Math. Soc. Japan27, 184?193 (1975).
5. H. P.Lotz, Uniform convergence of operators onL ? and similar spaces. Erscheint in Math. Z. (1983).