Lei Han, Wenying Lu, Yifang Han, Shuhua Li, Jianhua Yin, Jiaxin Xie, Tong Su, and Guangwen Cao, “Evolutionary characteristics of swine-origin H1N1 influenza virus that infected humans from sporadic to pandemic”, African Journal of Pig Farming, vol. 2, no. 1, pp. 1–17, May 2014.