@inproceedings{abiy1970exact,
title={Exact bounds for the continuous spectrum of certain differential eigenvalue problems},
author={Abiy Kifle},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203447449794154},
booktitle={Arkiv for Matematik},
volume={9},
number={1},
pages={197-204},
year={1970},
}
Abiy Kifle. Exact bounds for the continuous spectrum of certain differential eigenvalue problems. 1970. Vol. 9. In Arkiv for Matematik. pp.197-204. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203447449794154.