1. FAO 2007 FAOSTAT: Statistical Data Base of the FAO . http://faostat.fao.org/
2. FAO/UNESCO 2006
3. Changes in topsoil organic carbon of croplands in mainland China over the last two decades.;Huang;Chinese Science Bulletin,2006
4. IPCC 2008 Climatic Change 2007: The Physical Science Basis-Summary for Policymakers . Contribution of Working Group I to the fourth Assessment Report of the International Panel on Climate Change (eds S. Solomon et al. ). Cambridge University Press, Cambridge