@article{MAN_1991__289_4_164779,
     author = {Rainer Wittmann},
     title = {Hopfs ergodic theorem for nonlinear operators.},
     journal = {Mathematische Annalen},
     pages = {239--254},
     publisher = {mathdoc},
     volume = {289},
     number = {4},
     year = {1991},
     zbl = {0703.47042},
     url = {http://geodesic.mathdoc.fr/item/MAN_1991__289_4_164779/}
}