@book {156,
	title = {An Illustrated Flora of the Northern United States, Canada And The British Possessions},
	volume = {3},
	year = {1913},
	publisher = {Charles Scribner{\textquoteright}s Sons},
	organization = {Charles Scribner{\textquoteright}s Sons},
	edition = {2},
	author = {Nathaniel Lord Britton and Addison Brown}
}
@book {235,
	title = {An illustrated flora of the northern United States, Canada and the British possessions : from Newfoundland to the parallel of the southern boundary of Virginia, and from the Atlantic Ocean westward to the 102d meridian (1913)},
	year = {1913},
	publisher = {New York : C. Scribner{\textquoteright}s sons},
	organization = {New York : C. Scribner{\textquoteright}s sons},
	url = {http://www.archive.org/details/illustratedflora03brit},
	author = {Nathaniel Lord Britton and Addison Brown}
}
@book {262,
	title = {Illustrated Flora of the Northeastern United States and Adjacent Canada},
	series = {The Sympetalous Dicotyledoneae},
	volume = {3},
	year = {1952},
	pages = {503-505},
	publisher = {Hafner Press. A Division of Macmillian Publishing Co., INC},
	organization = {Hafner Press. A Division of Macmillian Publishing Co., INC},
	address = {New York},
	author = {Gleason, Henry A.}
}
@book {272,
	title = {An Encyclopedia of Shade perennials},
	year = {2002},
	pages = {173},
	publisher = {Timber Press, Inc},
	organization = {Timber Press, Inc},
	address = {Portland},
	author = {Schmid, W.George}
}
@book {218,
	title = {Flora of North America},
	series = {Magnoliophyta: Asteridae(in part): Asteraceae, part1},
	volume = {19},
	year = {2006},
	pages = {202-203},
	publisher = {Oxford University Press, Inc.},
	organization = {Oxford University Press, Inc.},
	address = {New York},
	url = {www.fna.org},
	author = {Strother, John L},
	editor = {Flora of north America Editorial Commitee ,}
}
