@article{DAN_1958_120_3_a15,
     author = {P. P. Kasyankov},
     title = {The conditions for the existence of a stigmatic image in electron optical systems having a curvilinear axis},
     journal = {Doklady Akademii Nauk},
     pages = {497--500},
     publisher = {mathdoc},
     volume = {120},
     number = {3},
     year = {1958},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1958_120_3_a15/}
}