Institution: | (1) Department of Mathematics, St Petersburg Technology Institute, Sankt Petersburg, Russia (e-mail: derk@tu.spb.ru) , RU;(2) Theoretical Physics Division, Department of Mathematical Sciences, University of Liverpool, Liverpool, L69 7ZF, United Kingdom (e-mail: jag@amtp.liv.ac.uk) , GB;(3) Department of Theoretical Physics, State University of St Petersburg, Sankt Petersburg, 198904 Russia (e-mail: manashov@snoopy.phys.spbu.ru) , RU |