@article{ELA_1998__3__a4,
     author = {Chien, Mao-Ting and Neumann, Michel},
     title = {Positive definiteness of tridiagonal matrices via the numerical range},
     journal = {The electronic journal of linear algebra},
     pages = {93--102},
     publisher = {mathdoc},
     volume = {3},
     year = {1998},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ELA_1998__3__a4/}
}