@inproceedings{a.1887sur,
title={Sur une question de maximum et de minimum},
author={A. Markoff},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108202945321977885},
booktitle={Acta Mathematica},
volume={9},
number={1},
pages={57-70},
year={1887},
}