@article{MAN_1981__256_163493,
     author = {Shmuel Kantorovitz},
     title = {Spectrality {Criteria} for {Unbounded} {Operators} with {Real} {Spectrum.}},
     journal = {Mathematische Annalen},
     pages = {19--28},
     year = {1981},
     volume = {256},
     zbl = {0459.47022},
     url = {http://geodesic.mathdoc.fr/item/MAN_1981__256_163493/}
}