Cobban, W. A. (1987). Some Middle Cenomanian (Upper Cretaceous) Acanthoceratid Ammonites, from the Western Interior of the United States: Ammonites of the genera Calycoceras, Acanthoceras, Plesiacanthoceras and Protacanthoceras from the Frontier Formation and equivalent rocks are described and illustrated. United States Gov. Print. Off.
Chicago-Zitierstil (17. Ausg.)Cobban, William A. Some Middle Cenomanian (Upper Cretaceous) Acanthoceratid Ammonites, from the Western Interior of the United States: Ammonites of the Genera Calycoceras, Acanthoceras, Plesiacanthoceras and Protacanthoceras from the Frontier Formation and Equivalent Rocks Are Described and Illustrated. Washington: United States Gov. Print. Off, 1987.
MLA-Zitierstil (9. Ausg.)Cobban, William A. Some Middle Cenomanian (Upper Cretaceous) Acanthoceratid Ammonites, from the Western Interior of the United States: Ammonites of the Genera Calycoceras, Acanthoceras, Plesiacanthoceras and Protacanthoceras from the Frontier Formation and Equivalent Rocks Are Described and Illustrated. United States Gov. Print. Off, 1987.