Agricultural development in Indonesia: current problems,issues and polices
 Artikel Jurnal
Boken, Vijendra K.
Monitoring and predicting agricultural drought: a global study
Oxford University Press, 2005
 Buku Teks
The study of society : methods and problems
edited by F.C. Bartlett
Kegan Paul, Trench, 1946
 Buku Teks
Yudelman, Montague
Africans on the land : economic problems of african agricultural development in Southeren,Central, and East Afric, Whit special reference to Southern Rhodesia
Harvard University Press , 1975
 Buku Teks
Barnes, Ralph M. (Ralph Mosser)
Motion and time study : problems and projects
John Wiley & Sons, 1949
 Buku Teks