Proceedings of ECOpole
Proceedings of ECOpole > 2015 > Vol. 9, No. 2 > 459--464
Proceedings of ECOpole > 2015 > Vol. 9, No. 2 > 473--481
Proceedings of ECOpole > 2015 > Vol. 9, No. 2 > 459--464
Proceedings of ECOpole > 2015 > Vol. 9, No. 2 > 473--481