Bing Chen 0001 Shaocheng Tong Xiaoping Liu 0004 Fuzzy approximate disturbance decoupling of MIMO nonlinear systems by backstepping approach. 1097-1125 2007 158 Fuzzy Sets Syst. 10 https://doi.org/10.1016/j.fss.2006.12.012 db/journals/fss/fss158.html#ChenTL07