@article{MOMA_1988__105_2_178385,
     author = {Rainer Wittmann},
     title = {Schwach irreduzible {Markoff-Operatoren.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {319--334},
     publisher = {mathdoc},
     volume = {105},
     number = {2},
     year = {1988},
     zbl = {0641.47038},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1988__105_2_178385/}
}