The Helderberg Group and the position of the Silurian-Devonian boundary in North America /
by Jean M. Berdan.
APA Citation
Berdan, J. Milton., Geological Survey (U.S.). (1964). The Helderberg Group and the position of the Silurian-Devonian boundary in North America. Washington, [D.C.]: United States Government Printing Office.
MLA Citation
Berdan, Jean Milton, and Geological Survey (U.S.). The Helderberg Group And the Position of the Silurian-Devonian Boundary In North America. Washington, [D.C.]: United States Government Printing Office, 1964.
Warning: These citations may not always be complete (especially for serials).