Kassim, A. ., S. . Yusuf, A. . Ussi, and M. . Omar. “Impact of Zanzibar Investment Promotion Authority Approved Projects on Gross Domestic Product of Zanzibar”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 56, no. 2, Mar. 2021, pp. 253-62, https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/12267.