Meghan G. Radtke; Kathleen B. Pigg; Wesley C. Wehr (2005), "Fossil Corylopsis and Fothergilla Leaves (Hamamelidaceae) from the Lower Eocene Flora of Republic, Washington, U.S.A., and Their Evolutionary and Biogeographic Significance", International Journal of Plant Sciences, 166 (2): 347, doi:10.1086/427483, S2CID20215269
Meghan G. Radtke; Kathleen B. Pigg; Wesley C. Wehr (2005), "Fossil Corylopsis and Fothergilla Leaves (Hamamelidaceae) from the Lower Eocene Flora of Republic, Washington, U.S.A., and Their Evolutionary and Biogeographic Significance", International Journal of Plant Sciences, 166 (2): 347, doi:10.1086/427483, S2CID20215269