@inproceedings{y.1980elliptic,
title={Elliptic systems in$H$_{$s,δ$}spaces on manifolds which are euclidean at infinity},
author={Y. Choquet-bruhat, and D. Christodoulou},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203253531740290},
booktitle={Acta Mathematica},
volume={146},
number={1},
pages={129-150},
year={1980},
}
Y. Choquet-bruhat, and D. Christodoulou. Elliptic systems in$H$_{$s,δ$}spaces on manifolds which are euclidean at infinity. 1980. Vol. 146. In Acta Mathematica. pp.129-150. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203253531740290.