Tozer, E.T. (1979). "The significance of the ammonoids Paratirolites and Otoceras in correlating the Permian–Triassic boundary beds of Iran and the People's Republic of China". Canadian Journal of Earth Sciences. 16 (7): 1524–1532. Bibcode:1979CaJES..16.1524T. doi:10.1139/e79-139.
Tozer, E.T. (1979). "The significance of the ammonoids Paratirolites and Otoceras in correlating the Permian–Triassic boundary beds of Iran and the People's Republic of China". Canadian Journal of Earth Sciences. 16 (7): 1524–1532. Bibcode:1979CaJES..16.1524T. doi:10.1139/e79-139.