Pengsisomboun, S., P. Paphaphanh, L. Kunyalong, N. Phongthady, V. Chansompou, and P. Phonpaserd. “Study of Spatial Distribution and Characteristics of Littering Spots in Houy-Markhiew Watershed, Vientiane Capital”. Souphanouvong University Journal Multidisciplinary Research and Development, vol. 8, no. 1, June 2022, pp. 144-53, http://www.su-journal.com/index.php/su/article/view/179.