@article{DIA_1997__37__3_0,
     author = {Ehresmann, Andr\'ee C.},
     title = {Colimits in free categories},
     journal = {Diagrammes},
     pages = {3--12},
     publisher = {Universit\'e Paris 7, Unit\'e d'enseignement et de recherche de math\'ematiques},
     volume = {37},
     year = {1997},
     mrnumber = {1677068},
     zbl = {0919.18002},
     language = {en},
     url = {http://www.numdam.org/item/DIA_1997__37__3_0/}
}