@article{PM_1992_1992_1_a39,
     author = {R{\'\i}o, Angel del},
     title = {M\'etodos categ\'oricos en teor{\'\i}a de anillos graduados.},
     journal = {Publicacions matem\`atiques},
     pages = {489-531},
     year = {1992},
     volume = {36},
     number = {2A},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PM_1992_1992_1_a39/}
}