（1）
Asymptotically perfect and relative convergence of productivityBart Hobijn1,*, Philip Hans Franses2
Journal of Applied EconometricsVolume 15, Issue 1, pages 59–81, January/February 2000


http://www3.interscience.wiley.com/journal/71000729/abstract

（2）
Convergence of productivity: a commentZijun Wang
Journal of Applied EconometricsVolume 21, Issue 7, pages 1101–1102, November 2006

http://onlinelibrary.wiley.com/doi/10.1002/jae.895/abstract