@inproceedings{p.1889sur,
title={Sur le mouvement d'un fil dans un plan fixe},
author={P. Appell},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108202947053173901},
booktitle={Acta Mathematica},
volume={12},
number={1},
pages={1-50},
year={1889},
}