@inproceedings{matti1979on,
title={On the existence of angular limits of$n$-dimensional quasiconformal mappings},
author={Matti Vuorinen},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203508551804335},
booktitle={Arkiv for Matematik},
volume={18},
number={1},
pages={157-180},
year={1979},
}
Matti Vuorinen. On the existence of angular limits of$n$-dimensional quasiconformal mappings. 1979. Vol. 18. In Arkiv for Matematik. pp.157-180. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203508551804335.