@article{GDZPPN002060094,
title = {Perturbation of Closed Operators and Their Adjoints.},
journal = {Commentarii mathematici Helvetici},
volume = {45},
year = {1970},
pages = {524-529},
zbl = {0263.47015},
url = {http://dml.mathdoc.fr/item/GDZPPN002060094}
}
Hess, Peter; Kato, Tosio. Perturbation of Closed Operators and Their Adjoints.. Commentarii mathematici Helvetici, Tome 45 (1970) pp. 524-529. http://gdmltest.u-ga.fr/item/GDZPPN002060094/