@article{RCM_1993__27_1-2_181884,
     author = {Jaime Rodr{\'\i}guez Montes},
     title = {Extreme points of numerical ranges of quasihyponormal operators},
     journal = {Revista colombiana de matematicas},
     pages = {223--230},
     publisher = {mathdoc},
     volume = {27},
     number = {1-2},
     year = {1993},
     zbl = {0811.47021},
     url = {http://geodesic.mathdoc.fr/item/RCM_1993__27_1-2_181884/}
}