M. Zolkipli, H., et al. “Spatial Variation and Possible Sources Assessment at Federal Territory of Kuala Lumpur Water Treatment Plan Using Chemometric Technique”. International Journal of Engineering and Technology, vol. 7, no. 4.34, Dec. 2018, pp. 70-74, https://doi.org/10.14419/ijet.v7i4.34.23583.