@inproceedings{james1964isolated,
title={Isolated singularities of solutions of quasi-linear equations},
author={James Serrin},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203205981813992},
booktitle={Acta Mathematica},
volume={113},
number={1},
pages={219-240},
year={1964},
}