Distribution of the sum-of-digits function of random integers: a survey
  We review some probabilistic properties of the sum-of-digits function of random integers. New asymptotic approximations to the total variation distance and its refinements are also derived. Four different approaches are used: a classical probability approach, Stein's method, an analytic approach and a new approach based on Krawtchouk polynomials and the Parseval identity. We also extend the study to a simple, general numeration system for which similar approximation theorems are derived. 
Louis H. Y. Chen, Hsien-Kuei Hwang and Vytas Zacharovas
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