Equation 6.7.72D5BD01BDC4D

\begin{equation} M_ u(a,r_2)-M_ u(a,r_1) =\int _{\log r_1^2}^{\log r_2^2}D_ u(a,\exp (t/2))\, \mathrm dt, \qquad 0<r_1<r_2<R. \end{equation}