We have information from several sources:
Elderberry as a Medicinal Plant—D. Charlebois
Temperate Berry Crops—Chad Finn
Sievers, A.F. 1930. The Herb Hunters Guide. Misc. Publ. No. 77. USDA, Washington DC.
Magness, J.R., G.M. Markle, C.C. Compton. 1971. Food and feed crops of the United States.