Affiliation: | a Mathematical Institute, Gdańsk University, ul. Wita Stwosza 57, 80-952 Gdańsk, Poland b Mathematical Institute, Polish Academy of Sciences, ul. ?niadeckich 8, 00-950 Warszawa, Poland c Department of Differential Equations, Gdańsk University of Technology, ul. Narutowicza 11/12, 80-952 Gdańsk, Poland d Faculty of Civil Engineering, Gdańsk University of Technology, ul. Narutowicza 11/12, 80-952 Gdańsk, Poland |