O. Arino et al., EXISTENCE OF PERIODIC-SOLUTIONS FOR DELAY-DIFFERENTIAL EQUATIONS WITHSTATE-DEPENDENT DELAY, Journal of differential equations, 144(2), 1998, pp. 263-301
In this paper we study the existence of periodic solutions of a delay
differential equation with delay depending indirectly on the state. A
fu;ed point problem related io a Poincare operator is constructed and
solved using an ejective fixed point theorem. (C) 1998 Academic Press.