@article{MAN_1977__231_163049,
     author = {George Luna},
     title = {On the {Numerical} {Range} in {Reflexive} {Banach} {Spaces.}},
     journal = {Mathematische Annalen},
     pages = {33--38},
     publisher = {mathdoc},
     volume = {231},
     year = {1977},
     zbl = {0347.46010},
     url = {http://geodesic.mathdoc.fr/item/MAN_1977__231_163049/}
}