title: A TWENTY-ONE-YEAR EXPERIENCE WITH ANTIGENIC VARIATION AMONG INFLUENZA B VIRUSES.
mesh_terms: D000940:Antigenic Variation; D000941:Antigens; D006385:Hemagglutination Inhibition Tests; D006801:Humans; D007106:Immune Sera; D009981:Influenza B virus; D009975:Orthomyxoviridae
chemical_list: D000941:Antigens; D007106:Immune Sera
keywords: ANTIGENS; HEMAGGLUTINATION INHIBITION TESTS; IMMUNE SERUMS; INFLUENZA VIRUSES