@article{MZ_1971__123_171621,
     author = {Reinhold B\"ohme},
     title = {Nichtlineare {St\"orung} der isolierten {Eigenwerte} selbstadjungierter {Operatoren.}},
     journal = {Mathematische Zeitschrift},
     pages = {61--92},
     publisher = {mathdoc},
     volume = {123},
     year = {1971},
     zbl = {0239.47042},
     url = {http://geodesic.mathdoc.fr/item/MZ_1971__123_171621/}
}