For Achillea
Arriagada, J.E., and N.G. Miller. 1997. The genera of Anthemidae (Compositae; Asteraceae) in the southeastern United States. Harvard Papers in Botany 2: 1-46.
Cronquist, A. 1980. Asteraceae, Volume I, Vascular flora of the Southeastern United States. University of North Carolina Press, Chapel Hill, N.C.
Guo, Y.-P., F. Ehrendorfer, and R. Samuel. 2004. Phylogeny and systematics of Achillea (Asteraceae-Anthemidae) inferred from nrITS and plastid trnL-F DNA sequences. Taxon 53: 657-672.
Guo, Y.-P., J. Saukel, R. Mittermayr, and F. Ehrendorfer. 2005. AFLP analyses demonstrate genetic divergence, hybridization, and multiple polyploidization in the evolution of Achillea (Asteraceae-Anthemideae). New Phytologist 166: 273-290.
Ramsey, J., A. Robertson, and B. Husband. 2008. Rapid adaptive divergence in New World Achillea, an autopolyploid complex of ecological races. Evolution 62-63: 639-653.
Trock, D.K. 2006a. Achillea. In Flora of North America Editorial Committee. 2006a. Flora of North America north of Mexico. Volume 19, Magnoliophyta: Asteridae, part 6: Asteraceae, part 1. Oxford Univ. Press, New York, NY. 579 pp.
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