Change and cause analysis of water resources in Fengtai district of Beijing in recent 61a (from 1956 to 2016)Jing Qin, Wen-long Niu, Wei Lu, Ling-yun Zhao and Wen-lian GaoMATEC Web Conf., 246 (2018) 02023DOI: https://doi.org/10.1051/matecconf/201824602023