@article{NUMA_1976__26_132404,
     author = {H. Schneider and B.D. Saunders},
     title = {A {Symmetric} {Numerical} {Range} for {Matrices.}},
     journal = {Numerische Mathematik},
     pages = {99--106},
     publisher = {mathdoc},
     volume = {26},
     year = {1976},
     zbl = {0312.65034},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1976__26_132404/}
}