Suppressing chaos in fractional-order systems by periodic perturbations on system variables Marius-F. Danca, Wallace K.S. Tang, Qingyun Wang and Guanrong Chen Eur. Phys. J. B, 86 3 (2013) 79 Published online: 04 March 2013 DOI: 10.1140/epjb/e2012-31008-0