@inproceedings{williamthe,
  title={The equivariant Dehn's lemma and loop theorem},
  author={William H Meeks, and Shing-Tung Yau},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191224203730069125077},
  booktitle={Commentarii Mathematici Helvetici},
  volume={56},
  number={1},
  pages={225-239},
}
             
            
                
William H Meeks, and Shing-Tung Yau. The equivariant Dehn's lemma and loop theorem. Vol. 56. In Commentarii Mathematici Helvetici. pp.225-239. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191224203730069125077.