1. T.M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, New York, 1976.
2. S. Chowla, On Kloosterman’s sum, Norske Vid. Selsk. Forhdl., 40:70–72, 1967.
3. W. Duke and H. Iwaniec, A Relation Between Cubic Exponential and Kloosterman Sums, AMS, Providence, RI, 1993.
4. T. Estermann, On Kloosterman’s sum, Mathematika, 8:83–86, 1961.
5. L.K. Hua, Introduction to Number Theory, Science Press, Peking, 1964.