@article{MAN_1911__70_158509,
     author = {E. Schmidt},
     title = {\"Uber eine {Klasse} linearer funktionaler {Differentialgleichungen}},
     journal = {Mathematische Annalen},
     pages = {499--524},
     year = {1911},
     volume = {70},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MAN_1911__70_158509/}
}