@inproceedings{j.1886sur,
title={Sur les unités électriques},
author={J. Bertrand},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108202940770641842},
booktitle={Acta Mathematica},
volume={8},
number={1},
pages={387-392},
year={1886},
}