@article{SM_2006_197_11_a4, author = {S. A. Stepanov}, title = {Method of orbit sums in the theory of }, journal = {Sbornik. Mathematics}, pages = {1635--1667}, publisher = {mathdoc}, volume = {197}, number = {11}, year = {2006}, language = {en}, url = {http://geodesic.mathdoc.fr/item/SM_2006_197_11_a4/} }