@article{NUMA_1974__22_132281,
     author = {R. Hettich},
     title = {Kriterien zweiter {Ordnung} f\"ur lokal beste {Approximationen.}},
     journal = {Numerische Mathematik},
     pages = {409--417},
     publisher = {mathdoc},
     volume = {22},
     year = {1974},
     zbl = {0276.41013},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1974__22_132281/}
}