	Authors	Year	Title
	Alberti, Groos-Uffenorde & Streel	1974	The stratigraphical significance of the Protognathodus fauna from Stockum (Devonian/Carboniferous boundary, Rhenish Schiefergebirge). Newsletters on Stratigraphy, 3,4: 263-276, fig.1,2; Leiden.
	Korn	1984a	Die Goniatiten der Stockumer Imitoceras-Kalklinsen (Ammonoidea; Devon/Karbon-Grenze). Courier Forschungsinstitut Senckenberg, 67: 71-89, fig.1-6, pl.1-4; Frankfurt a.M.