def METHOD_NAME(f1, f2, par, C):
    flavio.citations.register("Brivio:2017vri")
    i, j = sorted((_sectors['d'][f1], _sectors['d'][f2]))
    d_g = -(C['phid_{}{}'.format(i, j)] + C['phiq1_{}{}'.format(i, j)] + C['phiq3_{}{}'.format(i, j)]) / (4 * sqrt(2) * par['GF'])
    if i > j:
        d_g = d_g.conjugate()
    if f1 == f2:
        d_g += d_gZb(par, C) * gV_SM(f1, par) + 1 / 3 * d_sh2(par, C)
    return d_g