	Authors	Year	Title
	Bisat & Hudson	1943	The lower Reticuloceras (R1) goniatite succession in the Namurian of the North of England. Proceedings of the Yorkshire Geological Society, 24 (6): 383-440, fig.1, pl.23-30; Wakefield.
	Nikolaeva & Kullmann	1998	A review of Middle Namurian ammonoid biostratigraphy. Newsletters on Stratigraphy, 36: 117-144, 15 figs., Berlin, Stuttgart.