[1] N. DUNFORD J. T. SCHWARTZ: Linear Operators. Part 1, Interscience, New York, 1958.
[2] M. FALKOWITZ: 
On finite invariant measures for Markov operators. Proc. Amer. Math. Soc. 38 (1973), 553-557. 
MR 0312318[6] R. SINE: 
Convex combinations of uniformly mean stable Markov operators. Proc. Amer. Math. Soc. 51 (1975), 123-126. 
MR 0374943 | 
Zbl 0319.47005