MathSciDoc: An Archive for Mathematician ∫

@inproceedings{george1926an,
  title={An extension of Poincaré's last geometric theorem},
  author={George D. Birkhoff},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203043187592362},
  booktitle={Acta Mathematica},
  volume={47},
  number={4},
  pages={297-311},
  year={1926},
}