@inproceedings{rené1926sur,
title={Sur les systèmes adjoints d'équations différentielles linéaires},
author={René Lagrange},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203044300629371},
booktitle={Acta Mathematica},
volume={48},
number={1},
pages={179-201},
year={1926},
}