@inproceedings{d.1971on,
title={On the average order of the function $$E(x) = \sum\limits_{n \leqslant x} {\phi (n) - \frac{{3x^2 }}{{\pi ^2 }}} $$ },
author={D. Suryanarayana, and R. Sitaramachandra Rao},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203448951980167},
booktitle={Arkiv for Matematik},
volume={10},
number={1},
pages={99-106},
year={1971},
}
D. Suryanarayana, and R. Sitaramachandra Rao. On the average order of the function $$E(x) = \sum\limits_{n \leqslant x} {\phi (n) - \frac{{3x^2 }}{{\pi ^2 }}} $$ . 1971. Vol. 10. In Arkiv for Matematik. pp.99-106. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203448951980167.