1. Department of Applied Mechanics, Budapest University of Technology and Economics, Muegyetem rkp. 3, H1111 Budapest, Hungary
2. IK4-IDEKO Dynamics and Control Department, Arriaga Kalea 2, E20870 Elgoibar, Spain
3. School of Mathematics, Georgia Institute of Technology, 686 Cherry St NW, 30313 GA, Atlanta, USA