Hoffman, Michael E. Max Planck Institute for Mathematics, Max Planck Society;
http://dx.doi.org/10.1016/j.disc.2015.10.035 (出版社版)
Hoffman_Updown categories_oa_2016.pdf (全文テキスト(全般)), 280KB
Hoffman, M. E. (2016). Updown categories: generating functions and universal covers. Discrete Mathematics, 339(2), 906-922. doi:10.1016/j.disc.2015.10.035.