\chi_x^a \bar{\chi}_x^b \rangle 
& \equiv - \delta^{ab} \Sigma_x  
{\nonumber}\\  
&= \langle \chi_x^a \bar{\chi}_x^b \rangle_0 
{\nonumber}\\  
&
 + \sum_{\pm \mu} 
   (-1) (K \eta_{\mu,x})^2 
   \langle (\chi^a \bar{\chi})_x \rangle_0 
   U_{\mu,x} 
   \langle (\chi \bar{\chi})_{x+\hat{\mu}} \rangle_0 
   U_{\mu,x}^\dagger
   \langle (\chi \bar{\chi}^b)_x \rangle_0 
{\nonumber}\\  
&
 + \sum_{\substack{\pm \mu,\pm \nu \\ (\mu \neq \nu)}} 
   (-1) \left( 2K r i \eta_{\mu \nu,x} \displaystyle \frac {1}{2^3 \sqrt{3}} \right)^2 
   \langle (\chi^a \bar{\chi})_x \rangle_0 
   \mathcal{W}_{\mu\nu,x}^{(2)} 
   \langle (\chi \bar{\chi})_{x+\hat{\mu}+\hat{\nu}} \rangle_0 
   \mathcal{W}_{\mu\nu,x}^{(2)\dagger} 
   \langle (\chi \bar{\chi}^b)_x \rangle_0 
{\nonumber}\\  
&
 + \sum_{\pm \mu,\pm \nu} 
  (-1) (K \eta_{\mu,x})^2 (-1) (K \eta_{\nu,x})^2
  \langle (\chi^a \bar{\chi})_x \rangle_0 
  U_{\mu,x} 
  \langle (\chi \bar{\chi})_{x+\hat{\mu}} \rangle_0 
  U_{\mu,x}^\dagger
  \langle (\chi \bar{\chi})_x \rangle_0 U_{\nu,x} 
{\nonumber}\\  
& \times
  \langle (\chi \bar{\chi})_{x+\hat{\nu}} \rangle_0 
  U_{\nu,x}^\dagger
  \langle (\chi \bar{\chi}^b)_x \rangle_0 
{\nonumber}\\  
&
 + \sum_{\substack{\pm \mu,\pm \nu ,\pm \rho, \pm \sigma \\ (\mu \neq \nu, \rho \neq \sigma)}} 
   (-1) \left( 2K r i \eta_{\mu \nu,x} \displaystyle \frac {1}{2^3 \sqrt{3}} \right)^2 
   (-1) \left( 2K r i \eta_{\rho \sigma,x} \displaystyle \frac {1}{2^3 \sqrt{3}} \right)^2 
{\nonumber}\\  
& \times
   \langle (\chi^a \bar{\chi})_x \rangle_0 
   \mathcal{W}_{\mu\nu,x}^{(2)} 
   \langle (\chi \bar{\chi})_{x+\hat{\mu}+\hat{\nu}} \rangle_0 
   \mathcal{W}_{\mu\nu,x}^{(2)\dagger} 
   \langle (\chi \bar{\chi})_x \rangle_0  
   \mathcal{W}_{\rho\sigma,x}^{(2)} 
   \langle (\chi \bar{\chi})_{x+\hat{\rho}+\hat{\sigma}} \rangle_0 
   \mathcal{W}_{\rho\sigma,x}^{(2)\dagger} 
   \langle (\chi \bar{\chi}^b)_x \rangle_0 
{\nonumber}\\  
&
 + \sum_{\substack{\pm \mu,\pm \nu ,\pm \rho \\ (\mu \neq \nu)}} 
   (-1) \left( 2K r i \eta_{\mu \nu,x} \displaystyle \frac 