@inproceedings{h.1885über,
title={Über Systeme von Plancurven},
author={H. Krey},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108202937510774814},
booktitle={Acta Mathematica},
volume={7},
number={1},
pages={49-94},
year={1885},
}