Why does the productivity of education vary across individuals in Egypt? : firm size, gender, and access to technology as sources of heterogeneity in returns to education / Santiago Herrera; Karim Badr. Washington, DC : The World Bank, Middle East and North Africa Region, Poverty Reduction and Economic Management Unit, 2011 ; Halle (Saale) : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2011