(1)Minimum Lagrange Multiplier Unit Root Test with Two Structural Breaks
The Review of Economics and StatisticsVol. 85, No. 4 (Nov., 2003), pp. 1082-1089  

http://www.jstor.org/stable/3211829
(2)
Have Air Pollutant Emissions Converged among U. S. Regions? Evidence from Unit Root Tests

John A. List Southern Economic Journal Vol. 66, No. 1 (Jul., 1999), pp. 144-155   
• http://www.jstor.org/stable/1060840

（3）Evidence of panel stationarity from Chinese provincial and regional income
China Economic Review
Volume 19, Issue 2, June 2008, Pages 274-286
http://dx.doi.org/10.1016/j.chieco.2007.02.010