@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.