U.S. Department of Agriculture

Distribution of Tulip and Narcissus Bulbs in 1919, USDA Circular 65

The Production of Narcissus Bulbs, David Griffiths, 1924, USDA Bulletin 1270

Daffodils, David Griffiths, USDA Circular 122, October 1930, revised March 1934

Bulbs from Seed, David Griffiths, USDA Circular 311, June 1934

Speeding up Flowering in the Daffodil and the bulbous Iris, David Griffiths, USDA Circular 367, January 1936

Biology of the Narcissus Bulb Fly in the Pacific Northwest, Technical Bulletin No. 809, USDA, May 1942

Narcissus Bulb Fly, USDA, 1977