@article{TAC_2004_13_a3,
     author = {R.J.MacG. Dawson and R. Pare and D.A. Pronk},
     title = {Universal properties of {Span}},
     journal = {Theory and applications of categories},
     pages = {61--85},
     publisher = {mathdoc},
     volume = {13},
     year = {2004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2004_13_a3/}
}