1. Lucas S.G., Shen S., The Permian chronostratigraphic scale: history, status and prospectus (Geological Society, London 2016)
2. Ozhgibesov V.P., Kaffi R.J., Tectonics and palaeogeography of the Main Permian Field and the Perm Basin of the Colorado-Mexican Paraplatform in Modeling of geological systems and processes (Perm State Univ, Perm, 1996) (in Russian)
3. International Chronostratigraphic Chart. Version 01/2020.
4. Murchison's first sighting of the Permian, at Vyazniki in 1841
5. Collie M., Diemer J. (eds), Murchison’s wanderings in Russia. His geological exploration of Russia in Europe and the Ural Mountains, 1840 and 1841 (British Geological Survey, 2004)