@book{7973,
	author = {Gelʹfand, I. M. and Fomin, S. V.},
	title = {Calculus of variations},
	publisher = {Prentice-Hall},
	year = {1963},
	series = {Selected Russian publications in the mathematical sciences},
	address = {Englewood Cliffs, N.J.,},
	edition = {Rev. English ed.}
}