On the integral of the error term in the Dirichlet divisor problem
  Several results are obtained concerning the function $\Delta_k(x)$, which represents the error term in the general Dirichlet divisor problem. These include the estimates for the integral of this function, as well as for the corresponding mean square integral. The mean square integral of $\Delta_2(x)$ is investigated in detail. 
Aleksandar Ivic