4Barnard R D. An optimal-aim control strategy for nonlinear regulation systems[J]. IEEE Trans on Automatic Control, 1975, 20(2): 200-208.
5Barnard R D. Continuous-time implementation of optimal-aim controls[J]. IEEE Trans on Automatic Control, 1976, 21(3): 432-434.
6Barnard R D. Optimal-aim control strategies applied to large-scale nonlinear regulation and tracking systems[J]. IEEE Trans on Circuits and Systems, 1976, 23(12): 800-806.
7Meisel J. Transient stability augmentation using a hierarchical control structure[J]. IEEE Trans on Power Apparatus and Systems, 1980,99(1): 256-267.