Hildebrandt, G (1975). "Lichtelektrische Untersuchungen der vier Ap-Sterne HD 9531, HD 10221 HD 27309 und HD 184905". Astronomische Nachrichten. 295 (6): 277–280. Bibcode:1975AN....296..277H. doi:10.1002/asna.19752960605.
Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.
Hildebrandt, G (1975). "Lichtelektrische Untersuchungen der vier Ap-Sterne HD 9531, HD 10221 HD 27309 und HD 184905". Astronomische Nachrichten. 295 (6): 277–280. Bibcode:1975AN....296..277H. doi:10.1002/asna.19752960605.
Cowley, A.; et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal, 74: 375–406, Bibcode:1969AJ.....74..375C, doi:10.1086/110819.