1. Department of Software Engineering, Kaunas University of Technology, Studentų 50-415, Kaunas, Lithuania
2. Centre of Real Time Computer Systems, Kaunas University of Technology, K. Baršausko 59-A338, Kaunas, Lithuania
3. Institute of Mathematics, Silesian University of Technology, Kaszubska 23, 44-100 Gliwice, Poland