@article{DAN_1971_197_4_a5,
     author = {I. M. Gel'fand and V. A. Ponomarev},
     title = {Quadruples of subspaces of a finite-dimensional vector space},
     journal = {Doklady Akademii Nauk},
     pages = {762--765},
     publisher = {mathdoc},
     volume = {197},
     number = {4},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_197_4_a5/}
}