N. H. Hung*, 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 J. Earth Sci. 39 (2017) 76–86. DOI: https://doi.org/10.15625/0866-7187/39/1/9229.