1. On a class of differential-difference equations;Verblunsky,1956
2. Differential-Difference Equations;Bellman,1963
3. Introduction to the Theory of Fourier Integrals;Titchmarsh,1937
4. Solutions of some functional equations;Titchmarsh;J. London Math. Soc.,1939
5. The Laplace Transform;Widder,1946