Frederiksen, Norman. “19th Professor Birbal Sahni Memorial Lecture: Ratea of Floral Turnover and Diversity Change in the Fossil Records”. Journal of Palaeosciences 39, no. (1-3) (December 31, 1990): 127–139. Accessed May 16, 2024. https://jpsonline.co.in/index.php/jop/article/view/1686.