Sakke, Nordin, et al. “Aplikasi Kaedah Paras Ambang Dalam Menentukan Peristiwa Kemarau Di Lembangan Sungai Langat, Selangor, Malaysia: Application of Threshold Level Method in Determining Drought Events in The Sungai Langat Basin, Selangor, Malaysia”. Perspektif Jurnal Sains Sosial Dan Kemanusiaan, vol. 7, no. 3, Dec. 2015, pp. 47-58, https://ejournal.upsi.edu.my/index.php/PERS/article/view/1716.