@article{JETPL.93.726, title = {}, author = {Shikin, V.}, journal = {JETP Lett.}, volume = {93}, issue = {11}, pages = {648}, year = {2011}, doi = {}, url = {http://jetpletters.ru/ps/0/article_29314.shtml}, note = {[Pisma v ZhETF 93, 726 (2011)]} }