Kaplan, U., Kennedy, W., & Scheer, U. (2006). The Bottrop Formation ammonites, Campanian, western Munsterland.
Lua i Stíl Chicago (17ú heag.)Kaplan, UK, W. Kennedy, agus U. Scheer. The Bottrop Formation Ammonites, Campanian, Western Munsterland. 2006.
Lua MLA (9ú heag.)Kaplan, UK, et al. The Bottrop Formation Ammonites, Campanian, Western Munsterland. 2006.
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