1. Albeverio, S., Ma, Z.-M. R�ckner, M.: Non-symmetric Dirichlet forms and Markov processes on general state spaces. C.R. Acad. Sci. Paris S�r. A314, 77?82 (1992)
2. Aliprantis, C.D., Burkinshaw, O.: Positive operators. New York: Academic Press 1985
3. Amann, H.: Dual semigroups and second order linear elliptic boundary value problems. Isr. J. Math.45, 225?254 (1983)
4. Arendt, W.: Vector-valued Laplace transforms and Cauchy problems. Isr. J. Math.59, 327?352 (1987)
5. Arendt, W., Batty, C.J.K.: Exponential stability of a diffusion equation with absorption. J. Diff. Int. Eqn., to appear