@article{GDZPPN002320479, title = {Spectrality Criteria for Unbounded Operators with Real Spectrum.}, journal = {Mathematische Annalen}, volume = {255}, year = {1981}, pages = {19-28}, zbl = {0459.47022}, url = {http://dml.mathdoc.fr/item/GDZPPN002320479} }
Kantorovitz, Shmuel. Spectrality Criteria for Unbounded Operators with Real Spectrum.. Mathematische Annalen, Tome 255 (1981) pp. 19-28. http://gdmltest.u-ga.fr/item/GDZPPN002320479/