@article{TAC_2004_12_a6,
     author = {Susan Niefield},
     title = {Change of base for relational variable sets},
     journal = {Theory and applications of categories},
     pages = {248--261},
     publisher = {mathdoc},
     volume = {12},
     year = {2004},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2004_12_a6/}
}