@article{TAC_2004_12_a13,
     author = {John C. Baez and Aaron D. Lauda},
     title = {Higher-dimensional algebra {V:} {2-Groups}},
     journal = {Theory and applications of categories},
     pages = {423--491},
     publisher = {mathdoc},
     volume = {12},
     year = {2004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2004_12_a13/}
}