@article{RCM_1993_27_3-4_a4,
     author = {RAO DUGGIRALA K},
     title = {Rango num\'erico de productos conmutativos},
     journal = {Revista colombiana de matematicas},
     publisher = {mathdoc},
     volume = {27},
     number = {3-4},
     year = {1993},
     url = {http://geodesic.mathdoc.fr/item/RCM_1993_27_3-4_a4/}
}