@inproceedings{david1953the,
title={The space of groupoids over a compactum},
author={David Ellis, and Gaines Lang},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203137463855777},
booktitle={Acta Mathematica},
volume={89},
number={1},
pages={209-215},
year={1953},
}