@article{MAN_1922__85_158930,
     author = {R. Courant},
     title = {\"Uber die {L\"osungen} der {Differentialgleichungen} der {Physik.} {(I.} {Mitteilung)}},
     journal = {Mathematische Annalen},
     pages = {280--325},
     publisher = {mathdoc},
     volume = {85},
     year = {1922},
     zbl = {48.0560.02},
     url = {http://geodesic.mathdoc.fr/item/MAN_1922__85_158930/}
}