Y. Li et al., PERIODIC-SOLUTIONS FOR FUNCTIONAL-DIFFERENTIAL EQUATIONS WITH INFINITE LEAD AND DELAY, Applied mathematics and computation, 70(1), 1995, pp. 1-28
This paper discusses the existence of periodic solutions for functiona
l differential equations with infinite lead and delay. On the basis of
fixed point theorems, topological degree theories, comparison princip
les, and differential inequality methods, some general results are pro
ved.