Vellem, V., and L. Matezo Espoir. “The Impact of Aid for Trade on Horizontal and Vertical Export Diversification: The Case of Sub-Saharan Africa and Developing Asia”. International Journal of Research in Business and Social Science (2147- 4478), vol. 10, no. 5, Aug. 2021, pp. 135-47, doi:10.20525/ijrbs.v10i5.1296.