APA-referens (7:e uppl.)
Williams, D., & Butler, B. (2010). The Tallgrass Prairie Center guide to seed and seedling identification in the Upper Midwest. Published for the Tallgrass Prairie Center by the University of Iowa Press.
Chicago-referens (17:e uppl.)
Williams, Dave, och Brent Butler. The Tallgrass Prairie Center Guide to Seed and Seedling Identification in the Upper Midwest. Iowa City: Published for the Tallgrass Prairie Center by the University of Iowa Press, 2010.
MLA-referens (9:e uppl.)
Williams, Dave, och Brent Butler. The Tallgrass Prairie Center Guide to Seed and Seedling Identification in the Upper Midwest. Published for the Tallgrass Prairie Center by the University of Iowa Press, 2010.
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