1. Eccles, R.: Understanding the symptoms of the common cold and influenza. Lancet Infect. Dis. 5, 718–725 (2005). doi: 10.1016/S1473-3099(05)70270-X
2. http://www.who.int/topics/influenza/en/
3. http://www.who.int/mediacentre/factsheets/fs211/en/
4. http://www.cdc.gov/flu/about/viruses/index.htm
5. Webster, R.G., Laver, W.G.: Antigenic variation in influenza virus. Biology and chemistry. Prog. Med. Virol. 13, 271–338 (1971)