@article{JETPL.106.523, title = {}, author = {Yakushkin, E. D.}, journal = {JETP Lett.}, volume = {106}, issue = {8}, pages = {544}, year = {2017}, doi = {}, url = {http://jetpletters.ru/ps/dx/10.7868/S0370274X17200127}, note = {[Pisma v ZhETF 106, 523 (2017)]} }