©Copyright by the ODRA team, PJIIT, Warsaw, Poland. All rights reserved. Using this material for commercial purposes requires a written agreement of the team leader, Kazimierz Subieta. The material can be used without restriction for didactic purposes, can be changed, shortened and extended, under the condition that the name(s) of the original author(s) will be clearly, directly and explicitly associated with every adopted part of the material.