1. Agbu P A, James M E, 1994. The NOAA/NASA Pathfinder AVHRR Land Data Set User’s Manual. Goddard Distributed Active Archive Center, NASA, Goddard Space Flight Center, Greenbelt.
2. An Bujia, 2003. The cause and control measure for pastureland degradation in GerErMu city. Qinghai Prataculture, 12(2): 26–28. (in Chinese)
3. Bai Wanqi, Zhang Yili, Xie Gaodi et al., 2002. Analysis of formation causes of grassland degradation in Maduo County in the source region of the Yellow River. Chinese Journal of Applied Ecology, 13(7): 823–826. (in Chinese)
4. Chen Hui, Li Shuangcheng, Zheng Du, 2003. Features of ecosystems alongside Xining-Lhasa Highway and Railway and the impacts of road construction on them. Journal of Mountain Science, 21(5): 559–567. (in Chinese)
5. Gregori A D et al., 2000. Land Cover Classification System. Rome: Food and Agriculture Organization of the United Nations.