1. Aiswarya, V. S., Beyoola, W., Harsha, V. N., & Preethi, M. (2017). Palm oil fuel ash as partial replacement of cement in concrete. International Journal of Engineering Research & Technology, 6(3), 544–546.
2. Ariff, I. (2021). Free Malaysia Today (FMT) | free and Independent. Retrieved December 10, 2021, from https://www.freemalaysiatoday.com/category/nation/2021/01/23/after-mco-prices-of-materials-have-gone-sky-high-complain-builders/.
3. BS EN 12390-2:2009, Testing hardened concrete. Making and curing specimens for strength tests. British Standard, pp 1–12
4. BS EN 197-1. (2000). Cement - Part 1: Composition, specifications and conformity criteria for common cement. British Standard, pp. 1–45.
5. BS EN 1008. (2002). Mixing water for concrete - Specification for sampling, testing, and assessing the suitability of water, including water recovered from processes in the concrete industry, as mixing water for concrete. British Standard, pp. 1–23.