Utomo, S., and A. Sumarno. “The Effect of Additional Crystalline Materials on Concrete on Sulfic Acid”. IJIEEB International Journal of Integrated Education, Engineering and Business EISSN 2615-1596 PISSN 2615-2312, Vol. 4, no. 1, Mar. 2021, pp. 21-31, doi:10.29138/ijieeb.v4i2.1349.