@inproceedings{l.1991area,
title={Area integral estimates for solutions and normalized adjoint solutions to nondivergence form elliptic equations},
author={L. Escauriaza, and C. E. Kenig},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203540869724605},
booktitle={Arkiv for Matematik},
volume={31},
number={2},
pages={275-296},
year={1991},
}
L. Escauriaza, and C. E. Kenig. Area integral estimates for solutions and normalized adjoint solutions to nondivergence form elliptic equations. 1991. Vol. 31. In Arkiv for Matematik. pp.275-296. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203540869724605.