@article{PM_1994_1994_1_a28,
     author = {Cross, R. W.},
     title = {Operadores relativamente abiertos y concepto de ubicuidad.},
     journal = {Publicacions matem\`atiques},
     pages = {69-79},
     publisher = {mathdoc},
     volume = {38},
     number = {1},
     year = {1994},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PM_1994_1994_1_a28/}
}