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	publisher = {Charles Scribner{\textquoteright}s Sons},
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	edition = {2},
	author = {Nathaniel Lord Britton and Addison Brown}
}
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	address = {Leipzig},
	author = {Hoffmann, P.},
	editor = {Engler, A and K. Prantl}
}
@book {268,
	title = {Synoptical Flora of North America},
	volume = {2, Part 1},
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	author = {Asa Gray}
}
@article {117,
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	pages = {168-171},
	author = {Samuel B. Jones, Jr.}
}
@article {280,
	title = {Studies in the Anatomy and Morphology of the Composite Flower II. The Corollas of the Heliantheae and Mutisieae},
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	year = {1930},
	month = {12/1930},
	pages = {995-1010},
	author = {Minna Frotscher Koch}
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	title = {Ambrosanolides and other constituents of two rudbeckia species.},
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	volume = {56},
	year = {1990},
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@book {161,
	title = {Native American Ethnobotany},
	year = {1998},
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@book {218,
	title = {Flora of North America},
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	volume = {19},
	year = {2006},
	pages = {202-203},
	publisher = {Oxford University Press, Inc.},
	organization = {Oxford University Press, Inc.},
	address = {New York},
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	author = {Strother, John L},
	editor = {Flora of north America Editorial Commitee ,}
}
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	title = {Rudbeckia},
	booktitle = {Flora of North America},
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	year = {2006},
	author = {Lowell E. Urbatsch and Patricia B. Cox},
	editor = {Editorial Committee of Flora North America,}
}
@booklet {115,
	title = {The PLANTS Database},
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