@article{DAN_1972_203_2_a5,
     author = {V. K. Ionin},
     title = {Isoperimetric inequalities in simply connected {Riemann} spaces of nonpositive curvature},
     journal = {Doklady Akademii Nauk},
     pages = {282--284},
     publisher = {mathdoc},
     volume = {203},
     number = {2},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_203_2_a5/}
}