@article{TAC_2004_13_a8,
     author = {Stephen Lack},
     title = {Composing {PROPs}},
     journal = {Theory and applications of categories},
     pages = {147--163},
     year = {2004},
     volume = {13},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2004_13_a8/}
}