@article{JETPL.98.371, title = {}, author = {Kovalev, V. M. and Chaplik, A. V.}, journal = {JETP Lett.}, volume = {98}, issue = {6}, pages = {331}, year = {2013}, doi = {}, url = {http://jetpletters.ru/ps/dx/10.7868/S0370274X13180057}, note = {[Pisma v ZhETF 98, 371 (2013)]} }