Chao Lu Jennie Si Xiaorong Xie Jie Song Convergence of Direct Heuristic Dynamic Programming in Power System Stability Control. 908-913 2007 IJCNN http://dx.doi.org/10.1109/IJCNN.2007.4371079 conf/ijcnn/2007 db/conf/ijcnn/ijcnn2007.html#LuSXS07