Hieu, N., 		Phai, V., & 		Howard, L.
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 Cave systems in Phong Nha - Ke Bang area.
<em>VNU Journal Of Science: Earth And Environmental Sciences, 28</em>(4).
Retrieved from <a href="https://js.vnu.edu.vn/EES/article/view/1555" target="_new">https://js.vnu.edu.vn/EES/article/view/1555</a>