@inproceedings{james1954curve,
title={Curve families$F$^{*}locally the level curves of a pseudoharmonic function},
author={James Jenkins, and Marston Morse},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203138695312787},
booktitle={Acta Mathematica},
volume={91},
number={1},
pages={1-42},
year={1954},
}
James Jenkins, and Marston Morse. Curve families$F$^{*}locally the level curves of a pseudoharmonic function. 1954. Vol. 91. In Acta Mathematica. pp.1-42. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203138695312787.