C. Gunawan, L. K. Fung, L. Nul Hakim, E. Wahyudi, A. Pramana, and Y. Zalfiatri, “Paper Mill Sludge as a Substitute Material in Paving Blocks for a Sustainable Waste Management Approach”, jestm, vol. 5, no. 2, pp. 212–220, Sep. 2025.