Authors	Year	Title
Butcher & Hodson	1960	A Review of the Carboniferous Goniatite Zones in Devon and Cornwall. Palaeontology, 3 (1): 75-81, pl.17-19; London.
Gordon	1957	Mississippian Cephalopods of Northern and Eastern Alaska. Professional Papers, U.S. Geological Survey, 283: 1-61, fig.1-61, pl.1-6; Washington.
Korn	1997	The Palaeozoic ammonoids of the South Portuguese Zone. Memórias do Instituto geológico e Mineiro 33: 1-131, 69 text-figs., 16 pls., Lisboa.