On the zeros of subrange Jacobi polynomials

All positive zeros of subrange Jacobi polynomials, orthogonal on [−c, c], 0 < c < 1, with respect to the weight function w(x) = (1 − x)α(1 + x)β, α > − 1, β > − 1, are shown in the ultraspherical case α = β, and partly conjectured in the general case α < β, to be monotonically increasing as functions of c.