@article{JETPL.94.601, title = {}, author = {Kovalev, V. M. and Chaplik, A. V.}, journal = {JETP Lett.}, volume = {94}, issue = {7}, pages = {560}, year = {2011}, doi = {}, url = {http://jetpletters.ru/ps/0/article_29546.shtml}, note = {[Pisma v ZhETF 94, 601 (2011)]} }