Kathleen Weidner Zoehfeld. (2012). National Geographic Readers: Rocks and Minerals (39197th.). National Geographic Children's Books.
Lua i Stíl Chicago (17ú heag.)Kathleen Weidner Zoehfeld. National Geographic Readers: Rocks and Minerals. 39197th. National Geographic Children's Books, 2012.
Lua MLA (9ú heag.)Kathleen Weidner Zoehfeld. National Geographic Readers: Rocks and Minerals. 39197th. National Geographic Children's Books, 2012.
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