Multi-headed chimera states in coupled pendula P. Jaros, L. Borkowski, B. Witkowski, K. Czolczynski and T. Kapitaniak Eur. Phys. J. Special Topics, 224 8 (2015) 1605-1617 Published online: 27 July 2015 DOI: 10.1140/epjst/e2015-02483-x