I  held   several   research  positions  at  the   Institute of Mathematics    of   the   Siberian   branch    of   Russian Academy of  Sciences. Among  them, Research Fellow, and  from 1990  -  Chief  Research  Fellow. In the same time I  lectured   at   Novosibirsk  State University   for students mathematicians and later for students physicists (in Russia, very often  research and teaching appointments are different). Since 1993  I am Professor at  University  of Illinois  at  Urbana-Champaign. I   also held several  visiting  positions.  Among  them Guest Professor at   Max-Planck  Institut  fur  Mathematik at Bonn.