This entry contributed by Dana Romero
Physical constants are constants of nature encountered in physical problems, often also called "fundamental constants."
References
Abramowitz, M. and Stegun, C. A. (Eds.). "Physical Constants and Conversion Factors." Ch. 2 in Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables, 9th printing. New York: Dover, pp. 5-8, 1972.
Cohen, E. R. and Taylor, B. N. "The Fundamental Physical Constants." Physics Today, BG9-BG16, Aug. 1995.
Grigoriev, I. S. and Meilikhov, E. Z. (Eds.). Handbook of Physical Quantities. Boca Raton, FL: CRC Press, 1997.
NIST. "The NIST Reference on Constants, Units, and Uncertainty: Fundamental Physical Constants." http://physics.nist.gov/cuu/Constants/.
Weisstein, E. W. "Books about Physical Constants." http://www.ericweisstein.com/encyclopedias/books/PhysicalConstants.html.
