Smithsonian Institution
National Postal Museum: Art of the Stamp: Ira and George Gershwin
View the artwork for a U.S. postage stamp issued in 1999 to commemorate American composers George and Ira Gershwin. With a short passage highlighting their collaborated efforts.
Other
Gershwin fan.com
The site is a commercial one designed to sell Gershwin books, recordings, etc. Also included is great information on both George and Ira such as a detailed biography, photos, etc.