@article{MZM_1976_19_5_a14,
     author = {S. V. Buyalo},
     title = {An extremal theorem of {Riemannian} geometry},
     journal = {Matemati\v{c}eskie zametki},
     pages = {795--804},
     publisher = {mathdoc},
     volume = {19},
     number = {5},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1976_19_5_a14/}
}