A. K. Mohammed, M. S. S. Al_Salimi, and M. I. Ahmed, “INDOOR RADON-222 CONCENTRATION MEASUREMENTS AT FACULTY OF EDUCATION, YAFEA, ADEN UNIVERSITY, YEMEN, USING CR-39 NUCLEAR TRACK DETECTOR”, Electron. J. Univ. Aden Basic Appl. Sci., vol. 2, no. 4, pp. 161–168, Dec. 2021.