Wongso, Patrick Marcelino, et al. “Experimental Study of Concrete Composites of Fly Ash and Ferronickel Slag for Gamma-Ray Shielding”. Jurnal Ilmiah Aplikasi Isotop Dan Radiasi, vol. 16, no. 1, June 2020, pp. 31-36, doi:10.17146/jair.2020.16.1.5800.