@article{JRAM_1960__205_150455,
     author = {Eberhard Hopf},
     title = {On the {Ergodic} {Theorem} for {Positive} {Linear} {Operators.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {101--106},
     publisher = {mathdoc},
     volume = {205},
     year = {1960},
     zbl = {0103.33801},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1960__205_150455/}
}