Butler. The Tallgrass Prairie Center Guide to Seed and Seedling Identification in the Upper Midwest. University of Iowa Press.
Chicago-referens (17:e uppl.)Butler. The Tallgrass Prairie Center Guide to Seed and Seedling Identification in the Upper Midwest. University of Iowa Press.
MLA-referens (9:e uppl.)Butler. The Tallgrass Prairie Center Guide to Seed and Seedling Identification in the Upper Midwest. University of Iowa Press.
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