On Exponential Convergence of Gegenbauer Interpolation and Spectral   Differentiation
  This paper is devoted to a rigorous analysis of exponential convergence of polynomial interpolation and spectral differentiation based on the Gegenbauer-Gauss and Gegenbauer-Gauss-Lobatto points, when the underlying function is analytic on and within an ellipse. Sharp error estimates in the maximum norm are derived. 
Ziqing Xie, Li-Lian Wang and Xiaodan Zhao
math.NA