Fox,Charles. (1987). Introduction to the calculus of variations. Dover.
Dyfyniad Arddull ChicagoFox,Charles. Introduction to the Calculus of Variations. New York: Dover, 1987.
Dyfyniad MLAFox,Charles. Introduction to the Calculus of Variations. Dover, 1987.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.