@inproceedings{andreas1999deficient,
title={Deficient rational functions and Ahlfors's theory of covering surfaces},
author={Andreas Sauer},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203601388307766},
booktitle={Arkiv for Matematik},
volume={39},
number={1},
pages={151-155},
year={1999},
}
Andreas Sauer. Deficient rational functions and Ahlfors's theory of covering surfaces. 1999. Vol. 39. In Arkiv for Matematik. pp.151-155. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203601388307766.