1. B.C. Berndt, Ramanujan’s Notebooks, Part IV, Springer-Verlag, New York, 1994.
2. B.C. Berndt and R.A. Rankin, Ramanujan: Letters and Commentary, American Mathematical Society, Providence, RI, 1995; London Mathematical Society, London, 1995.
3. G.H. Hardy, On Dirichlet’s divisor problem, Proc. London Math. Soc. (2) 15 (1916), 1–25.
4. G.H. Hardy, Ramanujan, Cambridge University Press, Cambridge, 1940; reprinted by Chelsea, New York, 1960; reprinted by the American Mathematical Society, Providence, RI, 1999.
5. G.H. Hardy, Divergent Series, Clarendon Press, Oxford, 1949.