1. Binney, J., & Merrifield, M. 1998, Galactic Astronomy (Princeton: Princeton Univ. Press)
2. Binney, J., & Tremaine, S. 1987, Galactic Dynamics (Princeton: Princeton Univ. Press)
3. A CO survey of the southern Milky Way - The mean radial distribution of molecular clouds within the solar circle
4. Burton, W. B. 1992, in The Galactic Interstellar Medium, Saas-Fee Advanced course 21, ed. D. Pfenniger, & P. Bartholdi (Berlin: Springer)