@article{MAN_1980__247_163364,
     author = {Katsumi Nomizu and Marcos Dajczer},
     title = {On {Sectional} {Curvature} of {Indefinite} {Metrics,} {II.}},
     journal = {Mathematische Annalen},
     pages = {279--282},
     year = {1980},
     volume = {247},
     zbl = {0411.53010},
     url = {http://geodesic.mathdoc.fr/item/MAN_1980__247_163364/}
}