@inproceedings{s.1979minimal,
title={Minimal surfaces with free boundaries},
author={S. Hildebrandt, and J. C. C. Nitsche},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203250612364268},
booktitle={Acta Mathematica},
volume={143},
number={1},
pages={251-272},
year={1979},
}