Não informado. (1954). Virginia minerals. Department of Conservation and Development, Division of Geology.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Virginia Minerals. Charlottesville, Va: Department of Conservation and Development, Division of Geology, 1954.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Virginia Minerals. Department of Conservation and Development, Division of Geology, 1954.
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