Não informado. (1889). Bulletin of the Geological and Natural History Survey of Minnesota. Geological and Natural History Survey of Minnesota.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Bulletin of the Geological and Natural History Survey of Minnesota. Minneapolis, Minn: Geological and Natural History Survey of Minnesota, 1889.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Bulletin of the Geological and Natural History Survey of Minnesota. Geological and Natural History Survey of Minnesota, 1889.
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