@article{JETPL.97.344, title = {}, author = {Volovik, G. E. and Zubkov, M. A.}, journal = {JETP Lett.}, volume = {97}, issue = {6}, pages = {301}, year = {2013}, doi = {}, url = {http://jetpletters.ru/ps/0/article_30232.shtml}, note = {[Pisma v ZhETF 97, 344 (2013)]} }