1. Functional differential systems: Some models and perturbation problems;Cooke,1965
2. Periodic solutions of differential equations with time lag containing a small parameter;Perello;J. Diff. Eqs.,1968
3. Linear functional differential equations with constant coefficients;Hale;Cont. Diff. Eqs.,1963
4. Existence theory for a delay-differential system;Driver;Cont. Diff. Eqs.,1963
5. Differential Difference Equations;Bellman,1963