Gebremedhin, Berhanu; Pender, John; Girmay, Tesfaye(Environment and Production Technology Division, International Food Policy Research Institute, 2000)
Viana, Virgíllio; Grieg-Gran, Maryanne; Della Mea, Rosana; Ribenboim, Gabriel(International Institute for Environment and Development (IIED), London, 2009)
Schmithusen, Franz; Bisang, Kurt; Zimmermann, Willi(Policy and Institutions Branch, Policy and Planning Division, Food and Agriculture Organization of the United Nations, 2001)