@inproceedings{mats1964on,
title={On the existence of solutions of differential equations with constant coefficients},
author={Mats Neymark},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203432712617030},
booktitle={Arkiv for Matematik},
volume={5},
number={5},
pages={433-444},
year={1964},
}
Mats Neymark. On the existence of solutions of differential equations with constant coefficients. 1964. Vol. 5. In Arkiv for Matematik. pp.433-444. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203432712617030.