Van Tu, N., and L. Bounyavet. “DIVERSITY, DISTRIBUTION AND CONSERVATION OF RARE, ENDEMIC ORCHID SPECIES IN NAM NGUM UPSTREAM PROTECTION FOREST AREA OF XIENG KHOUANG PROVINCE, LAO PDR”. Journal of Forestry Science and Technology, no. 8, Nov. 2019, pp. 069-74, https://journal.vnuf.edu.vn/en/article/view/723.