@inproceedings{f.1964the,
title={The coefficients of quasiconformality of domains in space},
author={F. W. Gehring, and J. Väisälä},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203206222921994},
booktitle={Acta Mathematica},
volume={114},
number={1},
pages={1-70},
year={1964},
}
F. W. Gehring, and J. Väisälä. The coefficients of quasiconformality of domains in space. 1964. Vol. 114. In Acta Mathematica. pp.1-70. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203206222921994.