f <math><mfenced separators=""><mi>A</mi><mo>,</mo><mi>B</mi></mfenced></math>&#xa0;for which <math><mfenced open="|" close="|" separators=""><mi>&#x3bb;</mi></mfenced><mo>&lt;</mo><mn>6</mn></math>&#xa0;correspond to the top left diagonal elements of the generalized Schur form, <math><mfenced separators=""><mi>S</mi><mo>,</mo><mi>T</mi></mfenced></math>.  Estimates of the condition numbers for the selected eigenvalue cluster and corresponding deflating subspaces are also returned.</div><div class="paramtex