@article{NUMA_1965__7_131634,
     author = {H. SCHNEIDER},
     title = {Positive {Operators} and an {Inertia} {Theorem.}},
     journal = {Numerische Mathematik},
     pages = {11--17},
     year = {1965},
     volume = {7},
     zbl = {0158.28003},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1965__7_131634/}
}