@article{DAN_1957_114_2_a1,
     author = {S. A. Gel'fer},
     title = {On the maximum of the conformal radius of the fundamental region of a doubly-periodic group},
     journal = {Doklady Akademii Nauk},
     pages = {241--244},
     publisher = {mathdoc},
     volume = {114},
     number = {2},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_114_2_a1/}
}