@article{VMUMM_1994_5_a0,
     author = {Chan Fyong Zung},
     title = {Homotopy groups of the $3$-groupoid of regular {Ann-categories}},
     journal = {Vestnik Moskovskogo universiteta. Matematika, mehanika},
     pages = {3--6},
     year = {1994},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/VMUMM_1994_5_a0/}
}