Noramly, G., A. bin Hussin, C. V. C, and P. Siew Moi. “The Scientific, Social, Environmental and Economic Value of N.E. Langkawi: An Overview of the Present Status”. Malaysian Journal of Science, vol. 24, Apr. 2005, pp. 219-35, https://ejournal.um.edu.my/index.php/MJS/article/view/8848.