4) Centers for Disease Control and Prevention (CDC): Isolation of avian influenza A (H5N1) viruses from humans-Hong Kong, May-December 1997. MMWR Morb Mortal Wkly Rep 46: 1204-1207, 1997.
5) Saito T, et al: Characterization of a human H9N2 influenza virus isolated in Hong Kong. Vaccine 20: 125-133, 2001.