Department of Mathematics, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN, UK; Department of Mathematics, University of Białystok, K. Ciołkowskiego 1M, 15-245 Białystok, Poland
Prof. Tomasz Brzezinski
Department of Mathematics, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN, UK; Department of Mathematics, University of Białystok, K. Ciołkowskiego 1M, 15-245 Białystok, Poland