@article{MZ_1960__74_169877,
     author = {Lothar Collatz},
     title = {Monotone {Operatoren} bei {Anfangswertaufgaben} von {Differentialgleichungen.}},
     journal = {Mathematische Zeitschrift},
     pages = {158--166},
     publisher = {mathdoc},
     volume = {74},
     year = {1960},
     zbl = {0093.31102},
     url = {http://geodesic.mathdoc.fr/item/MZ_1960__74_169877/}
}