Zakharov Yuri D., Popov Alexander M., and Biakov Alexander S. “Late Permian to Middle Triassic Palaeogeographic Differentiation of Key Ammonoid Groups: Evidence from the Former USSR”. Polar Research 27, no. 3 (December 1, 2008): 441-468. Accessed April 19, 2024. https://polarresearch.net/index.php/polar/article/view/2900.