@book{29658,
	author = {Heikkila, Seppo. and Lakshmikantham, V.},
	title = {Monotone iterative techniques for discontinuous nonlinear differential equations /},
	publisher = {CRC Press,},
	year = {1994.},
	series = {Chapman & hall/crc pure and applied mathematics.},
	address = {[S.l.] :}
}