Abell, Geore O., Morrison, David, and Wolff, Sidney C.. Realm of the Universe. Saunders College Publishing, Fort Worth, TX:1994.

Berman, Louis and Evans, J. C.. Exploring the Cosmos. Little, Brown and Company, Boston:1986.

Chaisson, Eric and McMillan, Steve. Astronomy Today. Prentice Hall, Englewood Cliffs, NJ:1993.

De Vaucouleurs, G. The Cosmic Distance Scale and Hubble Constant. Australian National University, Canberra:1982.

Kauffman, William J. III. Universe. W. H. Freeman and Company, New York:1994.

Lemonick, Michael D.. The Light at the Edge of the Universe. Princeton University Press, Princeton, NJ:1993.

Pasachoff, Jay M.. Astronomy:From the Earth to the Universe. Saunders College Publishing, Philidelphia, Penn.:1991.

Peebles, P. J. E.. Principles of Physical Cosmology. Princeton University Press, Princeton, NJ:1993.

Riess, Adam G, Kirshner, Robert P., et all BVRI Light Curves for 22 Type Ia Supernovae. ApJ: 1998.

Shu, Frank H.. The Physical Universe An Introduction to Astronomy. University Science Books, Sausalito, CA:1982.

Silk, Joeseph. A Short History of the Universe. Scientific American Librairy, New York:1994.

Thurston, Wiiliam P. Three dimensional geometry and topology edited by Silvio Levy, Princeton University Press, Princeton, NJ: 1997.

Trimble, Virginia. "The 1920 Shapley-Curtis Discussion: Background, Issues, and Aftermath" Publications of the Astronomical Society of the Pacific 107: 1133-1144, 1995 December.

Wilson, Robert. Astronomy Through The Ages. Princeton University Press, Princeton, NJ:1997.