@article{TAC_2013_28_a12,
     author = {Tom Leinster},
     title = {Codensity and the ultrafilter monad},
     journal = {Theory and applications of categories},
     pages = {332--370},
     publisher = {mathdoc},
     volume = {28},
     year = {2013},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2013_28_a12/}
}