(en) Mary Lea Heger, « Further study of the sodium lines in class B stars ; The spectra of certain class B stars in the regions 5630A-6680A and 3280A-3380A ; Note on the spectrum of [gamma] Cassiopeiae between 5860A and 6600A », Lick Observatory Bulletin, vol. 10, no 337, , p. 146 (lire en ligne, consulté le )
