Krassilov, Valentin A., Sergey A. Afonin, and Sergey V. Naugolnykh. “Permotheca With in Situ Pollen Grains from the Lower Permian of the Urals”. Journal of Palaeosciences 48, no. (1-3) (December 31, 1999): 19–25. Accessed July 3, 2024. https://jpsonline.co.in/index.php/jop/article/view/1287.