V. Yu. Gusev, V. V. Zavialov, M. Yu. KozmanovVANT. Ser.: Mat. Mod. Fiz. Proc. 2003. No.2. С. 21-27.
A. D. Gadzhiev, V. V. Zavialov, A. A. ShestakovVANT. Ser.: Mat. Mod. Fiz. Proc 2009. No.2. С. 37-48.