1. 1 Faculty of Operation and Economics of Transport and Communications, University of Žilina, Univerzitná 8215/1, 010 26 Žilina; Slovakia +421/41 513 3411
2. 1 Faculty of Operation and Economics of Transport and Communications, University of Žilina, Univerzitná 8215/1, 010 26 Žilina; Slovakia +421/41 513 3407