USMAN, Hamza. Principals’ Effective Task Performance: A Tool for Proper Education Delivery in Nigerian Secondary Schools. Journal of Islamic Economics and Social Science (JIESS), Jakarta, Indonesia, v. 1, n. 2, p. 74–78, 2020. DOI: 10.22441/jiess.2020.v1i2.003. Disponível em: https://training-ojs3-publikasi.mercubuana.ac.id/index.php/jiess/article/view/jiess.2020.v1i2.003. Acesso em: 28 may. 2026.