@article{CHFMJ_2019_4_4_a9, author = {E. A. Belenkov and V. A. Greshnyakov}, title = {Theoretical investigation }, journal = {\v{C}el\^abinskij fiziko-matemati\v{c}eskij \v{z}urnal}, pages = {472--480}, publisher = {mathdoc}, volume = {4}, number = {4}, year = {2019}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/CHFMJ_2019_4_4_a9/} }