↑"Permian System (Zechstein of Germany—Magnesian limestone of England): Some introductory remarks explain why the authors have ventured to use a new name in reference to a group of rocks which, as a whole, they consider to be on the parallel of the Zechstein of Germany and magnesian limestone of England. They do so, not merely because a portion of deposits has long been known by the name "grits of Perm," but because, being enormously developed in the governments of Perm and Orenburg, they there assume a great variety of lithological features": R. I. Murchison, E. de Verneuil, A. von Keyserling, On the Geological Structure of the Central and Southern Regions of Russia in Europe and of the Ural Mountains (Londinii: Richard and John E. Taylor, 1842) p. 14
↑De historia nominis definitionisque vide: Mary Grace Wilmarth, The Geologic Time Classification of the United States Geological Survey Compared With Other Classifications, accompanied by the original definitions of era, period and epoch terms (United States Geological Survey Bulletin no. 769. Vasingtoniae: U.S. Government Printing Office, 1925) (p. 70 apud Google Books).