Onion Production Guide:A very complete guide for onion production. University of Georgia.
Allium cepa (Onion): Plants for a Future: description, botanic details, cultivation, uses, range.
Allium cepa proliferum (Tree Onion): Description, botanic details, cultivation, uses, and range.
Gernot Katzer's Spice Dictionary: Onions: Onion's main constituents, origin, ethymology, and how it is used for cooking around the world.
Green Onions: Guide for producing commercial green onions. University of Georgia.
History and Origin of the Onion: A tour of the history of onions in different cultures from ancient Egypt to modern times.
Onion and Garlic Research at the University of Liverpool: Research into flavor of Alliums using biochemical and molecular genetic methods, led by Dr. Hamish A. Collin and Dr. Meriel G. Jones.
Onion and Its Relatives: Articles about cultivated onions from Purdue University.
Onions and Related Species: Cultivating onions: fertility, planting, pest control, storage, varieties.