@article{DAN_1989_307_1_a1,
     author = {I. M. Grudskii},
     title = {The {Christoffel--Schwarz} formula for polyhedral surfaces},
     journal = {Doklady Akademii Nauk},
     pages = {15--17},
     publisher = {mathdoc},
     volume = {307},
     number = {1},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1989_307_1_a1/}
}