 Usage:  {wr, wi, z} = eisrg(a)  
 
 Input:

  a                      n x n matrix 
                         
 Output:

  wr                     n x 1 vector of real eigenvalues 
                         
  wi                     n x 1 vector of imaginary eigenvalues 
                         
  z                      n x n matrix of eigenvectors. 
                         
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(C) MD*TECH Method and Data Technologies, 17.8.2000
