Gray, R. O.; Napier, M. G.; Winkler, L. I. (2001), «The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars», The Astronomical Journal121 (4): 2148-2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.
Gray, R. O.; Napier, M. G.; Winkler, L. I. (2001), «The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. I. Precise Spectral Types for 372 Stars», The Astronomical Journal121 (4): 2148-2158, Bibcode:2001AJ....121.2148G, doi:10.1086/319956.