Não informado. (2004). Information Circular. Department of Natural Resources, Division of Geological Survey.
Chicago-Zitierstil (17. Ausg.)Não informado. Information Circular. Columbus, Ohio: Department of Natural Resources, Division of Geological Survey, 2004.
MLA-Zitierstil (8. Ausg.)Não informado. Information Circular. Department of Natural Resources, Division of Geological Survey, 2004.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.