1. Centre of Excellence for Vibro-Acoustic Systems and Signal Processing, Faculty of Technical Sciences, University of Novi Sad, Novi Sad 21215, Serbia
2. Department of Mathematics, Cornell University, Ithaca, NY 14853;
3. Department of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853
4. Technical University of Denmark, Department of Mechanical Engineering, Section of Solid Mechanics, Lyngby 2800, Denmark