def METHOD_NAME(f1, f2, par, C):
    flavio.citations.register("Brivio:2017vri")
    i, j = sorted((_sectors['u'][f1], _sectors['d'][f2]))
    sh2 = _sinthetahat2(par)
    sh = sqrt(sh2)
    ch = sqrt(1 - sh2)
    d_g = (C['phiq3_{}{}'.format(i, j)] + 1 / 2 * ch / sh * C['phiWB']) / (2 * sqrt(2) * par['GF']) - 1 / 4 * d_sh2(par, C) / sh**2
    return d_g