1. Oscillations in Nonlinear Systems;Hale,1963
2. Linear functional-differential equations with constant coefficients;Hale;Contrib. Differential Eqs.,1963
3. A Floquet theory for functional differential equations;Stokes,1962
4. On the Theory of Linear Differential Equations with Periodic Coefficients and Time Lag;Shimanov;Prikl. Mat. Meh.,1963
5. On the theory of linear differential equations with periodic coefficients and time lag