@inproceedings{g.1926some,
title={Some problems of diophantine approximation: An additional note on the trigonometrical series associated with the elliptic theta-functions},
author={G. H. Hardy, and J. E. Littlewood},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203042657982358},
booktitle={Acta Mathematica},
volume={47},
number={1},
pages={189-198},
year={1926},
}

G. H. Hardy, and J. E. Littlewood. Some problems of diophantine approximation: An additional note on the trigonometrical series associated with the elliptic theta-functions. 1926. Vol. 47. In Acta Mathematica. pp.189-198. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203042657982358.