@article{JETPL.106.282, title = {}, author = {Val?kov, V. V. and , }, journal = {JETP Lett.}, volume = {106}, issue = {5}, pages = {302}, year = {2017}, doi = {}, url = {http://jetpletters.ru/ps/dx/10.7868/S0370274X17170040}, note = {[Pisma v ZhETF 106, 282 (2017)]} }