@book{56229,
	author = {L Ė Ėlʹsgolʹt︠s︡ and L Ė Ėlʹsgolʹt︠s︡},
	title = {ifferential equations and the calculus of variations},
	publisher = {:Mir Publishers},
	year = {, 1970.},
	address = {Moscow, }
}