المؤلفون: Parsons, Christopher R.
URL الوصول: http://elibrary.worldbank.org/doi/pdf/10.1596/1813-9450-6034http://elibrary.worldbank.org/doi/abs/10.1596/1813-9450-6034
المؤلفون: Lopez-Calva, Luis F., Ortiz-Juarez, Eduardo
URL الوصول: http://elibrary.worldbank.org/doi/pdf/10.1596/1813-9450-5902http://elibrary.worldbank.org/doi/abs/10.1596/1813-9450-5902