Institution: | 1. Institute of Mathematics, State Academy of Sciences, Pyongyang, Democratic People''s Republic of Korea;2. PGItech Corp., Pyongyang, Democratic People''s Republic of Korea;3. Department of Mathematics, University of Paris VIII, F-93526 Saint-Denis, France;4. University Sorbonne Paris Cité, LAGA, UMR 7539, CNRS, 93430 Villetaneuse, France;5. Telecom Paris, Polytechnic Institute of Paris, 91120 Palaiseau, France |