@article{PM_1992_1992_1_a49,
     author = {Ion, Ion D. and Nita, Constantin},
     title = {Ultraproductos graduados. {Aplicaciones.}},
     journal = {Publicacions matem\`atiques},
     pages = {663-671},
     publisher = {mathdoc},
     volume = {36},
     number = {2A},
     year = {1992},
     language = {fr},
     url = {http://geodesic.mathdoc.fr/item/PM_1992_1992_1_a49/}
}