@article{AM2_1975__12_136510,
     author = {Frank Natterer},
     title = {Das {Randwertproblem} f\"ur eine {Klasse} singul\"arer gew\"ohnlicher {Differentialausdr\"ucke.}},
     journal = {Aequationes mathematicae},
     pages = {207--228},
     publisher = {mathdoc},
     volume = {12},
     year = {1975},
     zbl = {0312.34018},
     url = {http://geodesic.mathdoc.fr/item/AM2_1975__12_136510/}
}