@inproceedings{k.1975regularity,
title={Regularity for a class of non-linear elliptic systems},
author={K. Uhlenbeck},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203242486958219},
booktitle={Acta Mathematica},
volume={138},
number={1},
pages={219-240},
year={1975},
}