@inproceedings{e.1970a,
title={A problem on the union of Helson sets},
author={E. Galanis},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203447348909153},
booktitle={Arkiv for Matematik},
volume={9},
number={1},
pages={193-196},
year={1970},
}