1VLACHOS M, LIN J, KEOG E, et al. A wavelet-based any time algorithm for K-means clustering of time series[C]// Proc of 3 rd SIAM International Conference on Data Mining. San Francisco: [s. n.],2003.
2ZENG J, GUO D. A new clustering algorithm for time series analysis[M]. Berlin: Springer, 2006: 759-764.
3International Country Risk Guide. http://www.prsgroup. com/icrg.aspx.