- ^ (Firm), Infobase, film distributor. QA International, Galactic Clusters, OCLC 1048864075, retrieved 2022-03-09
{{citation}}: CS1 maint: multiple names: authors list (link) - ^ "Finite spherical systems – clusters of galaxies, galactic nuclei, globular clusters", Gravitational Physics of Stellar and Galactic Systems, Cambridge University Press, pp. 263–264, 1985-07-25, retrieved 2022-03-09
