[William C. Duckham delphinium trade circular and price list] - William C. Duckham Co.; Duckham, William C.; Henry G. Gilbert Nursery; Seed Trade Catalog Collection. (Madison, New Jersey, William C. Duckham, 1934, 1934)
https://www.biodiversitylibrary.org/bibliography/160384
Keywords: Delphinium|Madison|New Jersey|Nursery stock|Prices|