[1] Faculty of Engineering, Department of Industrial Engineering and Management, Lucian Blaga University of Sibiu, Sibiu, Romania
[2] Faculty of Mines, Department of Mining, Surveying and Civil Engineering, University of Petroşani, Petroşani, Romania
[3] Faculty of Engineering, North University Centre of Baia Mare, Department of Engineering and Technology Management, Technical University of Cluj-Napoca, Baia Mare, Romania