Forecasting reservoir monthly runoff via ensemble empirical mode decomposition and extreme learning machine optimized by an improved gravitational search algorithm. - Wen-jing Niu; Zhong-kai Feng; Ming Zeng; Bao-fei Feng; Yao-wu Min; Chun-Tian Cheng; Jian-zhong Zhou (Appl. Soft Comput., 2019)