@article{GDZPPN002218496, title = {\"Uber nichtlineare Spektral- und St\"orungstheorie.}, journal = {Manuscripta mathematica}, volume = {12}, year = {1974}, pages = {123-162}, zbl = {0295.47064}, url = {http://dml.mathdoc.fr/item/GDZPPN002218496} }
Singhof, Wilhelm. Über nichtlineare Spektral- und Störungstheorie.. Manuscripta mathematica, Tome 12 (1974) pp. 123-162. http://gdmltest.u-ga.fr/item/GDZPPN002218496/