Nghi, Tran, 		Phuong, Ta, 		Phai, Vu, 		Thanh, Dinh, 		Lan, Nguyen, 		Thai, Nguyen, AND 		Hong, Nguyen.
" Adventurous tourism-a potetial realm of world Natural Heritage - National Park Phong Nha - Ke Bang" <em>VNU Journal of Science: Earth and Environmental Sciences</em> [Online], Volume 27 Number 2 (15 June 2011)