@article{JETPL.97.248, title = {}, author = {, and , }, journal = {JETP Lett.}, volume = {97}, issue = {4}, pages = {220}, year = {2013}, doi = {}, url = {http://jetpletters.ru/ps/dx/10.7868/S0370274X13040115}, note = {[Pisma v ZhETF 97, 248 (2013)]} }