UN Industrial Development Organization, International Fertilizer Development Center (1998). The Fertilizer Manual (edisi ke-3rd). Springer. hlm. 46. ISBN0792350324.
Jeremy Woods, Adrian Williams, John K. Hughes, Mairi Black and Richard Murphy (August 2010). "Energy and the food system". Philosophical Transactions of the Royal Society. 365 (1554): 2991–3006. doi:10.1098/rstb.2010.0172.Pemeliharaan CS1: Banyak nama: authors list (link)
Conrad, David E. "Tenant Farming and Sharecropping". Encyclopedia of Oklahoma History and Culture. Oklahoma Historical Society. Diarsipkan dari versi asli tanggal 2013-05-27. Diakses tanggal 2013-09-16.
Jeremy Woods, Adrian Williams, John K. Hughes, Mairi Black and Richard Murphy (August 2010). "Energy and the food system". Philosophical Transactions of the Royal Society. 365 (1554): 2991–3006. doi:10.1098/rstb.2010.0172.Pemeliharaan CS1: Banyak nama: authors list (link)
Patrick Canning, Ainsley Charles, Sonya Huang, Karen R. Polenske, and Arnold Waters (2010). "Energy Use in the U.S. Food System". USDA Economic Research Service Report No. ERR-94. United States Department of Agriculture. Diarsipkan dari versi asli tanggal 2010-09-18. Diakses tanggal 2013-11-17.Pemeliharaan CS1: Banyak nama: authors list (link)
Steinfeld, H.; Gerber, P.; Wassenaar, T.; Castel, V.; Rosales, M.; de Haan, C. (2006). "Livestock's Long Shadow – Environmental issues and options"(PDF). Rome: U.N. Food and Agriculture Organization. Diarsipkan dari versi asli(PDF) tanggal 2008-06-25. Diakses tanggal 5 December 2008.
Steinfeld, H.; Gerber, P.; Wassenaar, T.; Castel, V.; Rosales, M.; de Haan, C. (2006). "Livestock's Long Shadow – Environmental issues and options"(PDF). Rome: U.N. Food and Agriculture Organization. Diarsipkan dari versi asli(PDF) tanggal 2008-06-25. Diakses tanggal 5 December 2008.
Patrick Canning, Ainsley Charles, Sonya Huang, Karen R. Polenske, and Arnold Waters (2010). "Energy Use in the U.S. Food System". USDA Economic Research Service Report No. ERR-94. United States Department of Agriculture. Diarsipkan dari versi asli tanggal 2010-09-18. Diakses tanggal 2013-11-17.Pemeliharaan CS1: Banyak nama: authors list (link)
"The global grain bubble". The Christian Science Monitor. 18 January 2008. Diarsipkan dari versi asli tanggal 2009-11-30. Diakses tanggal 2013-09-26.
Conrad, David E. "Tenant Farming and Sharecropping". Encyclopedia of Oklahoma History and Culture. Oklahoma Historical Society. Diarsipkan dari versi asli tanggal 2013-05-27. Diakses tanggal 2013-09-16.