some more goldenrod links
an iNat project on Euthamias - (the other goldenrods)
https://www.inaturalist.org/projects/systematic-evaluation-of-euthamia
an interactive key to solidagos from Canada and the US from the Shirley C. Tucker Herbarium
http://www.herbarium.lsu.edu/keys/solidago/solidago.html
Phylogenetics of Euthamia (Asteraceae: Astereae) and Asteromyia euthamiae
(Cecidomyiidae: Alycaulini)
Marisa Blake Szubryt
https://opensiuc.lib.siu.edu/uhp_theses/436/