@article{TAC_2010_24_a17,
     author = {John C. Baez and Alexander E. Hoffnung and Christopher D. Walker},
     title = {Higher {Dimensional} {Algebra} {VII:} {Groupoidification}},
     journal = {Theory and applications of categories},
     pages = {489--553},
     publisher = {mathdoc},
     volume = {24},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2010_24_a17/}
}