APA-čujuhus (7. p.)
Kesling, R. V. (1961). A new Species of Billingsites, an ascoceratid Cephalopod, from the upper ordovician ogontz formation of Michigan.
Chicago-čujuhus (17. p.)
Kesling, Robert V. A New Species of Billingsites, an Ascoceratid Cephalopod, from the Upper Ordovician Ogontz Formation of Michigan. 1961.
MLA-čujuhus (9. p.)
Kesling, Robert V. A New Species of Billingsites, an Ascoceratid Cephalopod, from the Upper Ordovician Ogontz Formation of Michigan. 1961.
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