EJIGU *, A. A. .; KETEMU, . D. G. .; ENDALEW, S. A. .; ASSEN, W. Y. . Challenges in Utilization of Precious Opal in Ethiopia: A Case Study from the Delanta Area, South Wollo, Ethiopia. Abyssinia Journal of Science and Technology, [S. l.], v. 5, n. 2, p. 14–21, 2020. DOI: 10.20372/ajst.2020.5.2.112. Disponível em: https://journals.wu.edu.et/index.php/ajst/article/view/112. Acesso em: 1 oct. 2022.