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Special Grassmann manifolds $$V^ 4_ 3$$ in the projective space $$P_ 7$$. (English) Zbl 0651.53008
There are studied 4-parameter families of 3-dimensional projective subspaces of projective 7-space with special focal properties.
Reviewer: R.Walter
##### MSC:
 53A20 Projective differential geometry 53A55 Differential invariants (local theory), geometric objects
##### Keywords:
systems of projective subspaces; focal properties
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