Chuah, C. H. ’, G. C.L. Eel, and S. Goh. “Ouregidione from Goniothalamus Velutinus (Annonaccae)”. Malaysian Journal of Science, vol. 18, no. 1, Apr. 1999, pp. 59-62, https://juku.um.edu.my/index.php/MJS/article/view/9390.