³⁸In more detail: For the second-order Taylor approximation in (76), we implicitly assume that the absolute value of the second-order term is much smaller than that of the ﬁrst-order one, i.e. $|ρ−1ℵ| ≥ |(ρ−1)(ρ−1 − 1)(ℵ2∕2)|$ . Substituting (77), the above could be simpliﬁed to $1 ≥ (− þφ∕℧)ω$ , therefore we have $ˆþφ < 0$ . This simple justiﬁcation is based on the conﬁdence that we have proved above that RIC and GIC $ΦΦΦ$ guarantee the denominator of the fraction in (73) is positive.