@article{DE_1975_11_5_a0,
     author = {N. P. Erugin},
     title = {The {Riemann} {problem.~I}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {771--781},
     publisher = {mathdoc},
     volume = {11},
     number = {5},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_5_a0/}
}