By Food and Agriculture Organization of the United Nations
By Hamdy A. Taha
By Neal Ford
By Robert Fritz
By Food and Agriculture Organization
By Neal Whitten
By Gibbs, Graham
By Jack Welch
By monocle
By Helen Peck, Martin Christopher, Moira Clark, Adrian Payne
By William J. Byrnes (Southern Utah University, USA)
By Bill Jelen, Tracy Syrstad