7David Bloom,, David Canning, Kevin Chan. Higher Education and Economic Development in Africa. www. worldbank. org/ afr/teia/pdfs/Higher_Education_Econ_Dev. pdf, 2006-9-23.
8David Bloom, David Canning, Kevin Chan. Higher Education and Economic Development in Africa [DB/OL].www. worldbank.org/afr/teia/pdfs/Higher_Education_Econ_Dev. pdf,2006-9-23.