 Usage:  yy=ivforec(h,yh,covdyd,z)  
 
 Input:

  h                      scalar, forecast horizon 
                         
  yh                     matrix, forecasts of variables 
                         
  covdyd                 matrix, forecast mse 
                         
  z                      scalar, 1.96 for alpha=0.95 
                         
 Output:

  yy                     matrix, forecast intervals 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
