@inproceedings{fr.1936sur, title={Sur les variétés à torsion nulle}, author={FR. Fabricius-Bjerre}, url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203107770853552}, booktitle={Acta Mathematica}, volume={66}, number={1}, pages={49-77}, year={1936}, }