1. F. Gantmakher and M. Krein,Oscillatory matrices and kernels and small vibrations of mechanical systems (in Russian), 2nd Ed. Moscow, 1950.
2. I. I. Hirschman and D. V. Widder,The convolution transform, Princeton, 1955.
3. Technical Report;S. Karlin,1958
4. I. P. Natanson,Konstruktive Funktionentheorie (Translation from Russian), Berlin, 1955.
5. G. Pólya and G. Szegö,Aufgaben und Lehrsätze aus der Analysis, vol. 2, Berlin, 1925.