@article{AM2_1969__2_182304,
     author = {F.F. BONSALL and B.E. CAIN and H. SCHNEIDER},
     title = {The {Numerical} {Range} of a {Continuous} {Mapping} of a {Normed} {Space}},
     journal = {Aequationes mathematicae},
     pages = {86--93},
     publisher = {mathdoc},
     volume = {2},
     year = {1969},
     zbl = {0162.20101},
     url = {http://geodesic.mathdoc.fr/item/AM2_1969__2_182304/}
}