1. A. Selberg, ?Harmonic analysis and discontinuous groups in weakly symmetric Riemannian spaces with applications to Dirichlet series,? J. Indian Math. Soc.,20, Nos. 1?3, 47?87 (1956).
2. D. A. Hejhal, ?The Selberg trace formula and the Riemann zeta function,? Duke Math J43, No. 3, 441?482 (1976).
3. Yu. V. Linnik, The Variance Method in Binary Additive Problems [in Russian], Leningrad State Univ. (1961).
4. C. Hooley, ?On the number of divisors of quadratic polynomials,? Acta Math.110, Nos. 1?2, 97?114 (1963).
5. A. Selberg, ?On the estimation of Fourier coefficients of modular forms,? in: Proc. Symp. Pure Math., Vol. 8, Number Theory, Am. Math. Soc., Providence, Rhode Island (1965), pp. 1?15.