@article{TAC_2013_28_a4,
     author = {Dominique Bourn},
     title = {On the monad of internal groupoids},
     journal = {Theory and applications of categories},
     pages = {150--65},
     year = {2013},
     volume = {28},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2013_28_a4/}
}