Better fit of codon usage of the polymerase and nucleoprotein genes to the chicken host for H7N9 than H9N2 AIVs. Issue 2 (August 2019) - Luo, Wen; Li, Yiliang; Yu, Shu; Shen, Xuejuan; Tian, Lin; Irwin, David M.; Shen, Yongyi