MathSciDoc: An Archive for Mathematician ∫

@inproceedings{herbert1948spaces,
  title={Spaces with non-positive curvature},
  author={Herbert Busemann},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203125126921685},
  booktitle={Acta Mathematica},
  volume={80},
  number={1},
  pages={259-310},
  year={1948},
}