@article{DAN_1970_193_2_a1,
     author = {I. M. Gel'fand and M. I. Graev and Z. Ya. Shapiro},
     title = {An integral geometry problem connected with a pair of {Grassmann} manifolds},
     journal = {Doklady Akademii Nauk},
     pages = {259--262},
     publisher = {mathdoc},
     volume = {193},
     number = {2},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1970_193_2_a1/}
}