Synchronization of two self-excited double pendula P. Koluda, P. Perlikowski, Krzysztof Czolczynski and T. Kapitaniak Eur. Phys. J. Special Topics, 223 4 (2014) 613-629 Published online: 28 April 2014 DOI: 10.1140/epjst/e2014-02129-7