2United States Department of Agriculture ( USDA ).Understanding USDA Crop Forecasts[R]. No 1554.
3Sushil Pradhan. Crop area estimation using GIS, remote sensing and area frame sampling[J]. JAG.2001,3(1):86-92
4Tsiligirides T A. Remote sensing as a tool for agricultural statistics :a case study of area frame sampling methodologyin Hellas[J].Computer and Electronics in Agriculture,1998,20:45--77.
5WANG Q F,XIAO L,LI J Y,et al.Land cover classification in Qinling Mountains in China,using time-series MODIS NDVI data[J].Proceedings of IGARSS 2008(DVD-ROM).IEEE International Volume,2008,4(7-11):766-769.
