The Rocky Mountain Journal of Mathematics
Two-point boundary value problems (BVPs) for delay differential equations have been studied extensively, beginning with the work of G. A. Kamenskiï, S. B. Norkin and others which was motivated by variational problems and problems in oscillation theory. L. J. Grimm and K. Schmitt and Ju. I. Kovac and L. I. Savcenko employed solutions of various differential inequalities for the study of two-point problems with retarded argument. In this paper, we show how a bilateral iteration procedure can be developed to yield existence and inclusion theorems for multipoint boundary value problems of conjugate type for nonlinear functional-differential equations.
Eloe, Paul W. and Grimm, Louis J., "Conjugate type boundary value problems for functional-differential equations" (1982). Mathematics Faculty Publications. 119.