1. Iterates of conditional expectation operators;Burkholder, D. L.;Proc. Amer. Math. Soc.,1961
2. A general ergodic theorem;Chacon, R. V.;Illinois J. Math.,1960
3. Reihe: Reelle Funktionen;Day, Mahlon M.,1958
4. 5. Dunford-Schwarz, Linear operators, Vol. I, Interscience, New York, 1958.