1. Maria Curie-Skłodowska University, Department of Logic and Cognitive Science, Maria Curie-Skłodowska Sq. 4, 20-031 Lublin, Poland. marcin.wolski@umcs.lublin.pl
2. University of Białystok, Faculty of Mathematics and Informatics, Konstantego Ciołkowskiego 1M, 15-245 Białystok, Poland. anna.gom@math.uwb.edu.pl