1. S. Agmon,Lectures on elliptic boundary value problems, Van Nostrand, New Jersey, 1965.
2. A. Beurling,A closure problem related to the Riemann zeta-function, Proc. Nat. Acad. Sci.41 (1955), 312?314.
3. A. Blanchard,Initiation à la theorie analytique des nombres, Dunod, Paris 1969.
4. R.P. Boas,Entire Functions, Academic Press, New York, 1954.
5. T. Carleman,Zur Theorie der linearen Integralengleichungen, Math. Z. 9 (1921), 196?217.