GrechnevaM. A., and StegantsevaP. G. 2016. “On the Existence of a Surface in the Pseudo-Euclidean space with Given Grassman Image”. Ukrains’kyi Matematychnyi Zhurnal 68 (10), 1320=1329. https://umj.imath.kiev.ua/index.php/umj/article/view/1923.