Changjiu Zhou Pik Kong Yue Jun Ni Shan-Ben Chan Dynamically stable gait planning for a humanoid robot to climb sloping surface. 341-346 2004 RAM http://ieeexplore.ieee.org/xpls/abs_all.jsp?isnumber=30991&arnumber=1438942&count=107&index=60 conf/ram/2004 db/conf/ram/ram2004.html#ZhouYNC04