@article{JETPL.109.219, title = {}, author = {Volkov, M. K. and Pivovarov, A. A.}, journal = {JETP Lett.}, volume = {109}, issue = {4}, pages = {222}, year = {2019}, doi = {}, url = {http://jetpletters.ru/ps/dx/10.1134/S0370274X19040027}, note = {[Pisma v ZhETF 109, 219 (2019)]} }