@article{GDZPPN002320622,
title = {Perturbations of Selfadjoint Operators with Point Spectra by Restrictions and Selfadjoint Extensions.},
journal = {Mathematische Annalen},
volume = {255},
year = {1981},
pages = {233-248},
zbl = {0443.47024},
url = {http://dml.mathdoc.fr/item/GDZPPN002320622}
}
Schmüdgen, Konrad. Perturbations of Selfadjoint Operators with Point Spectra by Restrictions and Selfadjoint Extensions.. Mathematische Annalen, Tome 255 (1981) pp. 233-248. http://gdmltest.u-ga.fr/item/GDZPPN002320622/