Bắc, Ä., & 		Khả, N.
(1993).
 Phân vùng địa hình Karst khối Bắc Sơn.
<em>VNU Journal Of Science: Natural Sciences And Technology, 9</em>(7).
Retrieved from <a href="https://js.vnu.edu.vn/NST/article/view/4389" target="_new">https://js.vnu.edu.vn/NST/article/view/4389</a>