S +=  traceColor(u_x2*Gamma(5) * quarkContract13(Gamma(5)*d_x2, insert_prop));
S -=  traceColor(u_x2*Gamma(5) * quarkContract13(Gamma(5)*d_x2, insert_prop));
LatticeSpinMatrix wallNuclUContract(const LatticePropagator& insert_prop,				    const Propagator& u_x2, 				    const Propagator& d_x2){  /* "\bar u O u" insertion in proton, ie. "(u C gamma_5 d) u" */  /* T = (1 + gamma_4) / 2 = (1 + Gamma(8)) / 2 */  /* C gamma_5 = Gamma(5) = - (C gamma_5)^T */  LatticeSpinMatrix  S;  // Term 1  S  = -traceColor(insert_prop * Gamma(5) * quarkContract13(Gamma(5)*d_x2, u_x2));  // Term 2  S -=  traceColor(u_x2 * traceSpin(quarkContract13(insert_prop*Gamma(5), Gamma(5)*d_x2)));  // Term 3  S -=  traceColor(insert_prop * traceSpin(quarkContract13(Gamma(5)*d_x2, u_x2*Gamma(5))));  // Term 4  S +=  traceColor(u_x2*Gamma(5) * quarkContract13(Gamma(5)*d_x2, insert_prop));  return S;}