Maul, E.; Eibach, R. (June 1999). "Vitis International Variety Catalogue". Information and Coordination Centre for Biological Diversity (IBV) of the Federal Agency for Agriculture and Food (BLE), Deichmanns Aue 29, 53179 Bonn, Germany. Archived from the original on 11 April 2007. Retrieved 2007-04-18.
slsa.sa.gov.au
Radden, Rosemary. "Grapes and Wines of the World". The State Library of South Australia, GPO Box 419, Adelaide SA 5001. Retrieved 2007-04-18.
web.archive.org
"Duetto". Casa Valduga. Archived from the original on 2007-08-15. Retrieved 2007-04-18.
Maul, E.; Eibach, R. (June 1999). "Vitis International Variety Catalogue". Information and Coordination Centre for Biological Diversity (IBV) of the Federal Agency for Agriculture and Food (BLE), Deichmanns Aue 29, 53179 Bonn, Germany. Archived from the original on 11 April 2007. Retrieved 2007-04-18.