@book{205047,
	author = {Kovacic, Ivana, and Wiley InterScience (Online service)},
	title = {The Duffing equation : nonlinear oscillators and their phenomena /},
	publisher = {Wiley,},
	year = {2011.},
	address = {Chichester, West Sussex, U.K. ;},
	url = {http://onlinelibrary.wiley.com/book/10.1002/9780470977859}
}