Matsitsi, S. M., et al. “Effects of Seasonal Change on the Levels of Geogenic Radionuclides in Sand and Rocks from Tyaa River Deposit in Kitui County: Geophysics”. International Journal of Fundamental Physical Sciences, vol. 9, no. 1, Mar. 2019, pp. 14-19, doi:10.14331/ijfps.2019.330124.