Influence of PPV, PRV and PRRSV on Efficacy of the Lapinized Hog Cholera Vaccine and Pathogenicity of Classical swine fever virus oleh Yi-bao NING, Yun ZHAO, Qin WANG, Xue-zheng FAN, Yu-ming QIN, Guang-chuan ZHANG, Lu XU, Hui-shen QIU, Zai-shi WANG, Li SONG, Qing-chun SHEN, Qi-zu ZHAO