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.
Outside links:
Butternut accessions from the National Germplasm Repository, Corvallis, Oregon