@article{MZM_1996_60_1_a0,
     author = {A. A. Borisenko},
     title = {On compact submanifolds of nonpositive external curvature in {Riemannian} spaces},
     journal = {Matemati\v{c}eskie zametki},
     pages = {3--10},
     publisher = {mathdoc},
     volume = {60},
     number = {1},
     year = {1996},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1996_60_1_a0/}
}