1. N.V. Azbelev, V.P. Maksimov, L.F. Rakhmatullina, Introduction to the theory of functional differential equations, Nauka, Moscow, 1991, in Russian.
2. E. Bravyi, R. Hakl, A. Lomtatidze, Optimal conditions for the unique solvability of the Cauchy problem for the first order linear functional differential equations, Czechoslovak Math. J., to appear.
3. R. Hakl, A. Lomtatidze, On a boundary value problem of periodic type for linear functional differential equations of the first order, Differentsial'nye Uravneniya., to appear.
4. R. Hakl, A. Lomtatidze, B. Půža, On a periodic boundary value problem for the first order scalar functional differential equation, J. Math. Anal. Appl., submitted.
5. Periodic and almost periodic solutions of functional-differential equations;Hale;Arch. Rational Mech. Anal.,1964