1. Allen, C. W. 1973, Astrophysical Quantities (3rd ed.; London: The Athlone Press)
2. Argue, A. N. 1963, MNRAS, 125, 557
3. Baade, D., et al., 1999, Messenger, 95, 15
4. Bernacca, P. L., Canton, G., Stagni, R., Leschiutta, S., & Sedmak, G. 1978, A&A, 70, 821
5. Bessell, M. S. 2005, ARAA, 43, 293