@article{TAC_2018_33_a0,
     author = {Daniel Cicala and Kenny Courser},
     title = {Spans of cospans in a topos},
     journal = {Theory and applications of categories},
     pages = {1--22},
     publisher = {mathdoc},
     volume = {33},
     year = {2018},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2018_33_a0/}
}