De Wilde, W. J., and B. E. Duyfjes. “Revision of Cyclocodon Griff. ex Hook.f. & Thomson (Campanulaceae)”.
Thai Forest Bulletin (Botany)
, no. 40, Nov. 2014, pp. 20-25, https://li01.tci-thaijo.org/index.php/ThaiForestBulletin/article/view/24122.