1. USDA; Economic Research Service; Washingtonc DC USA
2. Department of Agricultural Economics; Purdue University; West Lafayette IN USA
3. International Center for Agricultural Research in the Dry Areas (ICARDA); Amman Jordan
4. National Agricultural Research Center (NARC); Amman Jordan
5. National Institute for Agronomic Research in Tunisia (INRAT); Tunis Tunisia
6. Faculty of Agriculture; University of Jordan; Amman Jordan