This paper is concerned with the existence of extreme solutions of the periodic boundary value problems for a class of first order functional differential equations. We introduce new concept of lower and upper solutions and present that the method of lower and upper solutions coupled with monotone iterative technique is still valid. Meanwhile, we extend previous results. (c) 2004 Elsevier Inc. All rights reserved.
机构:
Univ Santiago de Compostela, Fac Matemat, Dept Anal Matemat, Santiago De Compostela 15782, SpainUniv Santiago de Compostela, Fac Matemat, Dept Anal Matemat, Santiago De Compostela 15782, Spain