OPIEW, Otojo; FEREDE, Bekalu; DAKSA, Dereje. The Principals. International Journal of Sciences: Basic and Applied Research (IJSBAR), Jordan, v. 34, n. 3, p. 88–108, 2017. Disponível em: https://gssrr.org/JournalOfBasicAndApplied/article/view/7528. Acesso em: 4 oct. 2025.