@inproceedings{w.1951sur,
title={Sur un probleme de la theorie des correspondances multivoques entre des ensembles abstraits},
author={W. Simonsen},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203130227748722},
booktitle={Acta Mathematica},
volume={84},
number={1},
pages={225-229},
year={1951},
}
W. Simonsen. Sur un probleme de la theorie des correspondances multivoques entre des ensembles abstraits. 1951. Vol. 84. In Acta Mathematica. pp.225-229. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203130227748722.