Hung*, N. H., N. T. Minh, D. D. Hung, and N. B. Hung. “New Discovery of Late Early Ordovician Graptolites and Discussion on Stratigraphic Sequence of Paleozoic Sediments in the Dinh Ca - Trang Xa Section, Vo Nhai Disctrict, Thai Nguyen Province, Northeast Vietnam”. Vietnam Journal of Earth Sciences, vol. 39, no. 1, Feb. 2017, pp. 76-86, doi:10.15625/0866-7187/39/1/9229.