Gerrienne, Philippe. “Abiostratigraphic Method Based on a Quantification of Fossil Tracheophyte Characters - Its Application to the Lower Devonian Posongchong Flora (Yunnan Province, China)”. Journal of Palaeosciences 45 (December 31, 1996): 194–200. Accessed May 1, 2024. https://www.jpsonline.co.in/index.php/jop/article/view/1233.