Litteratur
- Fullard , H. 1968 . China in Maps , London : George Philip & Son Ltd. .
- Heath , M. E. , Metcalfe , P. S. and Barnes , R. F. 1973 . Forages, the science of agriculture , Iowa , U.S.A. : The Iowa State University Press .
- Statistisk Sentralbyrå 1980 . Slatistisk Årbok 1980 . Oslo .
- World Atlas of Agriculture . 1973 . Asia and Oceania . 2 . Institute Geografico De Agostini , Novara , , Italy .