@inproceedings{gert1968fractional,
title={Fractional categories},
author={Gert Almkvist},
url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20170108203441023194099},
booktitle={Arkiv for Matematik},
volume={7},
number={5},
pages={449-476},
year={1968},
}