1. Allen, C. W. 1973, Astrophysical quantities (London: University of London, Athlone Press), 3rd ed.
2. The existence and shapes of dust lanes in galactic bars
3. Positions of Emission Nebulae in M31.
4. Binney, J., & Merrifield, M. 1998, Galactic astronomy (Princeton, NJ: Princeton University Press)