text: integral in the SCS at T = 0 and in the NS extrapolated 
  to T = 0 and compare the cut oﬀ eﬀect ∆f (ωc) to ∆WK 
  term. We also analyze the sign of ∆W (ωc) at large fre- 
  quencies and discuss under what conditions theoretical 
  W (∞) increases in the SCS. 
  
  We perform calculations for four models. First is a 
  conventional BCS model with impurities (BCSI model). 
  Second is an Einstein boson (EB) model of fermions in- 
  teracting with a single Einstein boson whose propaga- 
  tor does not change between NS and SCS. These two 
  cases will illustrate a conventional idea of the spectral 
  weight in SCS being less than in NS. Then we con- 
  sider two more sophisticated models: a phenomenological 
  “marginal Fermi liquid with impurities” (MFLI) model 
  of Norman and P´epin30, and a microscopic collective bo- 
  son (CB) model31 in which in the NS fermions interact 
  with a gapless continuum of bosonic excitations, but in a 
  d−wave SCS a gapless continuum splits into a resonance 
  and a gaped continuum. This model describes, in par- 
  ticular, interaction of fermions with their own collective 
  spin ﬂuctuations32 via 