Scientific collaboration
 Czech Technical University, Prague
 Ecole Polytechnique Federale de Lausanne, Lausanne
 Departamento de Fisica, Cinvestav, Mexico City
 Steklov Institute of Mathematics of Russian Academy of Sciences, Moscow
 Moscow State University, Faculty of Mechanics and Mathematics, Moscow
 Moscow Humanitarian University, Moscow
 Warsaw University, Department of Mathematical Methods in Physics (KMMF), Warszawa
 University of Sheffield, Sheffield
 Institute of Mathematics "S. Stoilow" of the Romanian Academy
