@inproceedings{jan1964on,
title={On the intersection of classes of infinitely differentiable functions},
author={Jan Boman},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203431594325020},
booktitle={Arkiv for Matematik},
volume={5},
number={3},
pages={301-309},
year={1964},
}
Jan Boman. On the intersection of classes of infinitely differentiable functions. 1964. Vol. 5. In Arkiv for Matematik. pp.301-309. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203431594325020.