 Usage:  y = archest(xx,q,p)  
 
 Input:

  xx                     vector 
                         
  q                      1 or 2 (can be extended) 
                         
  p                      1 or 2 (can be extended) 
                         
 Output:

  y                      list containing 1. parameter estimates, 2. standard 
                         errors, 3. likelihood value, 4. volatility estimate 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
