A generalization of the method of upper and lower solutions for discontinuous first order problems with nonlinear boundary conditions

In this paper we prove the existence of extremal solutions for a discontinu ous BVP between a lower and an upper solution which may be discontinuous in a finite set of points, Furthermore we present a monotone method with whic h we can explicitly construct a pair of sequences that converge to the extr emal solutions, despite the discontinuities of the right hand side of the e quation, (C) 2000 Elsevier Science Inc. All rights reserved.