@article{02125657,
title = {Universal properties of Span.},
journal = {Theory and Applications of Categories [electronic only]},
volume = {12},
year = {2004},
pages = {61-85},
zbl = {1062.18005},
language = {en},
url = {http://dml.mathdoc.fr/item/02125657}
}
Dawson, R.J.MacG.; Paré, R.; Pronk , D.A. Universal properties of Span.. Theory and Applications of Categories [electronic only], Tome 12 (2004) pp. 61-85. http://gdmltest.u-ga.fr/item/02125657/