Kathleen Weidner Zoehfeld. (2012). National Geographic Readers: Rocks and Minerals (39197th.). National Geographic Children's Books.
Chicago-referens (17:e uppl.)Kathleen Weidner Zoehfeld. National Geographic Readers: Rocks and Minerals. 39197th. National Geographic Children's Books, 2012.
MLA-referens (9:e uppl.)Kathleen Weidner Zoehfeld. National Geographic Readers: Rocks and Minerals. 39197th. National Geographic Children's Books, 2012.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.