Lankford, F. G. J., & Clark, J. R. (1961). Essential mathematics. Harcourt Brace and World.
Dyfyniad Arddull ChicagoLankford, Francis G. Jr, and J. R. Clark. Essential Mathematics. New York: Harcourt Brace and World, 1961.
Dyfyniad MLALankford, Francis G. Jr, and J. R. Clark. Essential Mathematics. Harcourt Brace and World, 1961.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.