% FIGURE 5.3.3
      function OMEGA = OMEGA533(IDER,X)
      global N
%                              EVALUATE OMEGA (IDER=0) OR ITS IDER-TH
%                              DERIVATIVE AT X
      OMEGA = 0.5*HERM('H',0,IDER,X) - 0.5*HERM('H',N,IDER,X);