@inproceedings{g.1942on,
title={On the theory of interpolation},
author={G. Grünwald},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203119560635643},
booktitle={Acta Mathematica},
volume={75},
number={1},
pages={219-245},
year={1942},
}