@article{MAN_1951__123_160256,
     author = {E. Heinz},
     title = {Beitr\"age zur {St\"orungstheorie} der {Spektralzerlegung.}},
     journal = {Mathematische Annalen},
     pages = {415--438},
     year = {1951},
     volume = {123},
     zbl = {0043.32603},
     url = {http://geodesic.mathdoc.fr/item/MAN_1951__123_160256/}
}