FORGHA, Njimanted G.; MBELLA, Mukete Emmanuel; NGANGNCHI, Forbe H. International Journal of Sciences: Basic and Applied Research (IJSBAR), Jordan, v. 21, n. 1, p. 287–303, 2015. Disponível em: https://www.gssrr.org/JournalOfBasicAndApplied/article/view/3517. Acesso em: 14 sep. 2025.