@article{JETPL.104.74, title = {}, author = {, }, journal = {JETP Lett.}, volume = {104}, issue = {2}, pages = {75}, year = {2016}, doi = {}, url = {http://jetpletters.ru/ps/dx/10.7868/S0370274X16140022}, note = {[Pisma v ZhETF 104, 74 (2016)]} }