	Authors	Year	Title
	Ehiro & Misaki	2005	Middle Permian ammonoids from the Kamiyasse-Imo district in the Southern Kitakami Massif, Northeast Japan. Paleontological Research, 9: 1-14, 9 fig.
	Zhou, Glenister & Furnish	1989	Two-fold or three-fold - concerning geological time-scale of Permian period. Acta Paleontologica Sinica, 28 (3): 269-282,fig.1-4, tab.1-4; Beijing.