@article{JETPL.93.797, title = {}, author = {, and Fraerman, A. A.}, journal = {JETP Lett.}, volume = {93}, issue = {12}, pages = {716}, year = {2011}, doi = {}, url = {http://jetpletters.ru/ps/0/article_29412.shtml}, note = {[Pisma v ZhETF 93, 797 (2011)]} }