@article{SLC_1985_13_a4,
     author = {Flavio Bonetti and Nino Civolani},
     title = {Some {Operations} on {Tolerances}},
     journal = {S\'eminaire lotharingien de combinatoire},
     year = {1985},
     volume = {13},
     url = {http://geodesic.mathdoc.fr/item/SLC_1985_13_a4/}
}