@article{JRAM_1981__323_152332,
     author = {U. Krengel and M.A. Akcoglu},
     title = {Ergodic theorems for superadditive processes.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {53--67},
     publisher = {mathdoc},
     volume = {323},
     year = {1981},
     zbl = {0453.60039},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1981__323_152332/}
}