PHUC, Nguyen Van.
 Ordovician - Silurian and Lower Devonian Graptolite Bearing Beds from Vietnam.
<strong>VNU Journal of Science: Natural Sciences and Technology</strong>, [S.l.], v. 18, n. 1, mar. 2002.
ISSN 2588-1140.
Available at: &lt;<a href="https://js.vnu.edu.vn/NST/article/view/3089" target="_new">https://js.vnu.edu.vn/NST/article/view/3089</a>&gt;. Date accessed: 23 nov. 2024.