@inproceedings{sara2001infinitely,
title={Infinitely many solutions of a symmetric semilinear elliptic equation on an unbounded domain},
author={Sara Maad},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203606321809805},
booktitle={Arkiv for Matematik},
volume={41},
number={1},
pages={105-114},
year={2001},
}

Sara Maad. Infinitely many solutions of a symmetric semilinear elliptic equation on an unbounded domain. 2001. Vol. 41. In Arkiv for Matematik. pp.105-114. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203606321809805.