1. |
E. T. Ivlev, È. M. Kondakova, G. G. Pustynnikov, “A projectively invariant class of manifolds of nondegenerate null pairs in multidimensional projective space”, Izv. Vyssh. Uchebn. Zaved. Mat., 1976, no. 11, 38–47 ; Soviet Math. (Iz. VUZ), 20:11 (1978), 34–41 |