“…On the other hand, we can always assume that ω 0 is a positive function, because for every Chebyshev system (ω 0 , ω 1 ), there exists α, β ∈ R such that αω 0 + βω 1 > 0 (cf. [2][3][4]). In the sequel, for fixed x, y ∈ I , the partial functions u → Ω (u, y) and u → Ω (x, u) will be denoted by Ω (·, y) and Ω (x, ·), respectively.…”