Rizal, M., S. N. Fadhila, and Prihantini. “Cluster Analysis Using Hierarchic Method for Classification of District / City of North Kalimantan Province Based on Human Development Indicators (HDI)”. Proceeding International Conference on Science and Engineering, vol. 4, Feb. 2021, pp. 235-9, http://sunankalijaga.org/prosiding/index.php/icse/article/view/665.