@inproceedings{henrik1908les, title={Les dérivées premiéres et secondes du potentiel}, author={Henrik Petrini}, url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203020559640186}, booktitle={Acta Mathematica}, volume={31}, number={1}, pages={127-332}, year={1908}, }