Yawo, Okwet, and Ita Akpan. “Assessment of Heavy Metals Concentration in Sediments of Utibete River, Eastern Obolo, Southeastern Nigeria Using Particle Induced X-Ray Emission (PIXE) Technique”. Researchers Journal of Science and Technology, vol. 1, no. 1, Dec. 2021, pp. 17-36, https://rejost.com.ng/index.php/home/article/view/4.