@article{ZVMMF_1987_27_5_a0,
     author = {A. L. Ageev},
     title = {The method of quasi-solutions for the problem of determining the eigenfunctions of a linear operator},
     journal = {\v{Z}urnal vy\v{c}islitelʹnoj matematiki i matemati\v{c}eskoj fiziki},
     pages = {643--650},
     year = {1987},
     volume = {27},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZVMMF_1987_27_5_a0/}
}