1. 题目：The measurement of rank mobility
    作者：Marcello D'Agostino and Valentino Dardanoni
    期刊：Jonrnal of Economic theory
               vol 144, issues 4, July 2009, pp1783-1803.
2. 题目：Measurement of income mobility: a re-examination
    作者：Kai-yuen Tsui
    期刊：Social choice and welfare
                vol 33, No 4, 2009
   相关链接：http://www.springerlink.com/content/p33367p0025j1p01/