Woltjer, L. (1968). Galaxies and the universe. Columbia University Press.
Lua i Stíl Chicago (17ú heag.)Woltjer, L. Galaxies and the Universe. New York: Columbia University Press, 1968.
Lua MLA (9ú heag.)Woltjer, L. Galaxies and the Universe. Columbia University Press, 1968.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.