@article{JETPL.93.51, title = {}, author = {Belavin, A. and , and , }, journal = {JETP Lett.}, volume = {93}, issue = {2}, pages = {47}, year = {2011}, doi = {}, url = {http://jetpletters.ru/ps/0/article_29108.shtml}, note = {[Pisma v ZhETF 93, 51 (2011)]} }