“…Extended interpolation is of interest in the field of the polynomial approximation since it introduces new systems of "good" interpolation knots (see for instance [4], [3], [2], [5], [27], [29], [16] and the references therein) and the research of "well far apart" zeros of orthogonal polynomials is still an open problem [9]. On the other hand, following a procedure proposed in [26] for the automatic estimate of the numerical error by extended Gaussian rules, extended interpolation can be used in the numerical evaluation of the convergence order in interpolation processes (see for instance [4]). Moreover extended matrices of orthogonal polynomials can be employed, for instance, in the approximation of singular and hypersingular integral transforms [28], [8].…”