Não informado. (1889). Bulletin of the Geological and Natural History Survey of Minnesota. Geological and Natural History Survey of Minnesota.
Chicago-referens (17:e uppl.)Não informado. Bulletin of the Geological and Natural History Survey of Minnesota. Minneapolis, Minn: Geological and Natural History Survey of Minnesota, 1889.
MLA-referens (8:e uppl.)Não informado. Bulletin of the Geological and Natural History Survey of Minnesota. Geological and Natural History Survey of Minnesota, 1889.
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