@book{8316,
	author = {Lefschetz, Solomon, and Cesari, Lamberto.},
	title = {Contributions to the theory of nonlinear oscillations /},
	publisher = {Princeton University Press,},
	year = {1956.},
	series = {Annals of mathematics studies,},
	address = {Princeton :},
	note = {Vol. 5 edited by L. Cesari, J. LaSalle, and S. Lefschetz.}
}