@article{JRAM_1985__358_152717,
     author = {J.F. Voloch and D. Koutroufiotis},
     title = {Saddle surfaces admitting local support planes.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {1--5},
     publisher = {mathdoc},
     volume = {358},
     year = {1985},
     zbl = {0551.53004},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1985__358_152717/}
}