@article{GDZPPN00202442X, title = {Bounds for the Second Eigenvalue of a Positive Operator. (Short Communication).}, journal = {Aequationes mathematicae}, volume = {5}, year = {1970}, pages = {397-397}, url = {http://dml.mathdoc.fr/item/GDZPPN00202442X} }
Hadeler, K.P. Bounds for the Second Eigenvalue of a Positive Operator. (Short Communication).. Aequationes mathematicae, Tome 5 (1970) p. 397. http://gdmltest.u-ga.fr/item/GDZPPN00202442X/