Phong, Nguyen Xuan, Nguyen Ngoc, Cu Minh Hoang, Le Hai An, and Hoang Ngoc Dang. 2016. “Biostratigraphy of Tri Ton Carbonate Formation, South of Song Hong Basin”. Petrovietnam Journal 7 (July), 40-47. http://www.pvj.com.vn/index.php/TCDK/article/view/531.