“…So, by (4) For the case of ϕ, ψ ∈ C − sm (I), since −ϕ, −ψ ∈ C + sm (I), it follows from the above discussion that a function s → x∇ t,−ξ s y is strictly monotone increasing on [0, 1]. However, by Lemma 3-(i), x∇ t,−ξ s y = x∇ t,ξ s y, where t (0, 1) and x, y I with x ≠ y, and then we obtain the desired result.…”