各位童鞋，我对数据做ADF检验，结果是一阶差分后不存在单位根，滞后做协整检验的时候滞后区间该如何确定呢？
Date: 03/29/10   Time: 16:49     
Sample: 1 31     
Included observations: 30     
Series: LNGDP LNEX LNG      
Lags interval: No lags     
     
Selected (0.05 level*) Number of Cointegrating Relations by Model     
     
Data Trend: None None Linear Linear Quadratic
Test Type No Intercept Intercept Intercept Intercept Intercept
No Trend No Trend No Trend Trend Trend
Trace 1 2 2 2 1
Max-Eig 1 2 2 2 1
     
*Critical values based on MacKinnon-Haug-Michelis (1999)     
     
Information Criteria by Rank and Model     
     
Data Trend: None None Linear Linear Quadratic
Rank or No Intercept Intercept Intercept Intercept Intercept
No. of CEs No Trend No Trend No Trend Trend Trend
     
  Log Likelihood by Rank (rows) and Model (columns)   
0  53.22376  53.22376  91.36022  91.36022  100.1249
1  94.82977  101.5301  111.6919  113.0327  121.0898
2  99.14631  117.2222  121.4808  123.3823  125.1869
3  100.2557  121.4873  121.4873  126.7520  126.7520
     
  Akaike Information Criteria by Rank (rows) and Model (columns)   
0 -3.548251 -3.548251 -5.890681 -5.890681 -6.274996
1 -5.921985 -6.302004 -6.846125 -6.868847  -7.272652*
2 -5.809754 -6.881477 -7.098720 -7.092153 -7.145792
3 -5.483714 -6.699152 -6.699152 -6.850133 -6.850133
     
  Schwarz Criteria by Rank (rows) and Model (columns)   
0 -3.548251 -3.548251 -5.750562 -5.750562 -5.994757
1 -5.641745 -5.975058 -6.425766 -6.401781 -6.712173*
2 -5.249275 -6.227585 -6.398121 -6.298141 -6.305073
3 -4.642996 -5.718314 -5.718314 -5.729175 -5.729175
     
这是我取滞后区间为（0  0）的时候得到的结果

是什么意思呢？求高手指点