Shinya Aoi Yuuki Sato Kazuo Tsuchiya Investigation of the effects on stability of foot rolling motion based on a simnle walking model. 2987-2992 2007 IROS http://dx.doi.org/10.1109/IROS.2007.4399303 conf/iros/2007 db/conf/iros/iros2007.html#AoiST07