Agency for Agricultural Research and Development Ministry of Agriculture, 1992
Buku Referensi
Ika Darnhofer, editor
[, Springer], 2012
eBooks
Cirad, 1999
Buku Teks SO
Bird, Richard M.
Harvard University Press, 1974
Buku Teks
Pusat Penelitian dan Pengabdian kepada Masyarakat (P3M) Politeknik Pertanian Negeri Payakumbuh,
Majalah, Jurnal, Buletin