Existence and comparison results for operator and differential equations in abstract spaces

In this paper we apply the chain methods developed in (Heikkilä and Lakshmikantham, 1994) to obtain new fixed point theorems and new existence and comparison results for operator equations in partially ordered sets. These results are then applied to discontinuous implicit functional differential equations in ordered Banach spaces.  2002 Elsevier Science (USA). All rights reserved.