Chapin, Suzanne, et al.  Middle Grades Math:  Tools for Success.  Needham, MA:
    Prentice Hall, 1999. p.286-389.

Chapin, Suzanne, et al.  Middle Grades Mathematics:  An Interactive Approach.
    Needham, MA:  Prentice Hall, 1994. p.44-89, 190-232.

DeSilva, Suranthe & D'Andreti, Peter. (1997). "Seeing Is Believing". [On-Line].
    Available: http://library.advanced.org/10030/index.htm.

Eschbach, Barbara.  Strengthening Your Geometry Program: Ideas, Strategies, and
    Hands-On Activities (Grades 7-12).  Pennsylvania: 1998.

Hirsch, E.D., Kett, Joseph, & Trefil, James.  The Dictionary of Cultural Literacy:
    What Every American Needs to Know.  Boston:  Houghton Mifflin Company,
    1988. p.448, 450.

Musser, Gary & Burger, William.  Mathematics for Elementary Teachers. Upper
    Saddle River, NJ: Prentice Hall, 1997. p.507, 509, 583, 661.

Woodard, Mark. (1995). "Furman University Mathematical Quotations Server".
    [On-Line] Available: http://math.furman.edu/~mwoodard/mquot.html