Chai Peng, Lee, and Meor Hakif Hassan. 2005. “Contributions from the Geology of Northeast Langkawi to Refining the Mid-Palaeozoic Stratigraphy and Palaeogeography of Peninsular Malaysia”. Malaysian Journal of Science 24 (April):15-23. https://juku.um.edu.my/index.php/MJS/article/view/8814.