@inproceedings{e.1891sur,
title={Sur la courbure des surfaces},
author={E. Catalan},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108202953243870957},
booktitle={Acta Mathematica},
volume={15},
number={1},
pages={191-192},
year={1891},
}