@inproceedings{per1970on,
title={On a problem of Smirnov},
author={Per Enflo},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203443870329125},
booktitle={Arkiv for Matematik},
volume={8},
number={2},
pages={107-109},
year={1970},
}