@article{DAN_1957_113_5_a1,
     author = {R. G. Barantsev},
     title = {A~boundary problem for equation $\psi_{\sigma\sigma}-K(\sigma)\psi_{\theta\theta}=0$ values given on the characteristic and $\sigma=\operatorname{const}$ lines},
     journal = {Doklady Akademii Nauk},
     pages = {955--958},
     publisher = {mathdoc},
     volume = {113},
     number = {5},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_113_5_a1/}
}