@inproceedings{john1985approximation,
title={Approximation of Sobolev functions in Jordan domains},
author={John L. Lewis},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203524800356468},
booktitle={Arkiv for Matematik},
volume={25},
number={1},
pages={255-264},
year={1985},
}