1. Differential-Difference Equations;Bellman,1963
2. On the limit of solutions of differential-difference equations as the retardation approaches zero;Bellman,1959
3. Singular perturbations of systems with retarded argument;Halanay;Rev. Math. Pures Appl.,1962
4. Periodic and almost periodic solutions of functional-differential equations;Hale;Arch. Rat. Mech. Anal.,1964
5. Linear functional-differential equations with constant coefficients;Hale;Cont. Diff. Equations,1964