Riemann-Hilbert analysis for a Nikishin system
  In this paper we give the asymptotic behavior of type I multiple orthogonal polynomials for a Nikishin system of order two with two disjoint intervals. We use the Riemann-Hilbert problem for multiple orthogonal polynomials and the steepest descent analysis for oscillatory Riemann-Hilbert problems to obtain the asymptotic behavior in all relevant regions of the complex plane. 
Guillermo L\'opez Lagomasino, Walter Van Assche
math.CA