For Epipactis
Brown, P.M., and G.W. Argus. 2002. Epipactis. In Flora of North America Editorial Committee. 2002a. Flora of North America north of Mexico. Volume 26, Magnoliophyta: Liliidae: Liliales and Orchidales. Oxford Univ. Press, New York, NY. 723 pp.
Correll, D.S. 1950. Native orchids of North America north of Mexico. Chronica Botanica Cp., Waltham, MA. 399 pp.
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