7Niu Z G, Zhang H Y, Gong P. More protection for China's wetlands. Nature, 2011, 471: 305.
8Gong P, Wang J, Yu L, et al. Finer resolution observation and monitoring of global land cover: First mapping results with Landsat TM and ETM+ data. Int J Remote Sens, 2013, 34: 2607-2654.