Jigui Jian Yanjun Shen Hui Yu Synchronization of Rikitake Chaotic Attractor via Partial System States. 2919-2924 2008 ICYCS http://dx.doi.org/10.1109/ICYCS.2008.148 conf/icycs/2008 db/conf/icycs/icycs2008.html#JianSY08