@inproceedings{tero1989pointwise,
title={Pointwise regularity of solutions to nonlinear double obstacle problems},
author={Tero Kilpeläinen, and William P. Ziemer},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203534594774553},
booktitle={Arkiv for Matematik},
volume={29},
number={1},
pages={83-106},
year={1989},
}
Tero Kilpeläinen, and William P. Ziemer. Pointwise regularity of solutions to nonlinear double obstacle problems. 1989. Vol. 29. In Arkiv for Matematik. pp.83-106. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203534594774553.