“…In light of its systematic design fashion and simplicity in real-time implementation [1,4,6], a number of elegant works dedicated to SDRE design for various practical nonlinear systems have been presented in the literature; see, for example, previous works [7][8][9][10][11][12][13][14][15][16] and the references therein. However, as shown in previous works [1,2,4], the abundantly existing SDRE-based practical/application results have drastically outpaced their available theoretical foundation, including global stability, optimality, etc.…”