@article{TAC_2010_23_a9,
     author = {Elisabeth Burroni and Jacques Penon},
     title = {A metric tangential calculus},
     journal = {Theory and applications of categories},
     pages = {199--220},
     publisher = {mathdoc},
     volume = {23},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/TAC_2010_23_a9/}
}