@article{AM2_1977__16_136693,
     author = {Marvin Marcus},
     title = {Pencils of real symmetric matrices and the numerical range. {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {193--193},
     publisher = {mathdoc},
     volume = {16},
     year = {1977},
     url = {http://geodesic.mathdoc.fr/item/AM2_1977__16_136693/}
}