Institution: | 1. Department of Mathematics and Informatics, Vilnius University, Naugarduko 24, Vilnius LT-03225, Lithuania;2. Faculty of Mathematics and Computer Science, Adam Mickiewicz University, Umultowska 87, 61-614 Poznań, Poland;3. Departamento de Matemática, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal;4. Institute of Mathematics and Informatics, Akademijos 4, Vilnius LT-08663, Lithuania |