Euphorbia in the Pacific States
This paper includes notes concerning species of Euphorbia occurring in or reported from the Pacific States (California, Oregon, and Washington), a key to all the native or naturalized species occurring in this area, and an alphabetized cross-referenced list of the valid species and their synonyms.
Wheeler, Louis C.
"Euphorbia in the Pacific States,"
Bulletin of the Southern California Academy of Sciences:
Available at: https://scholar.oxy.edu/scas/vol35/iss2/9