Asymptotic zero distribution of biorthogonal polynomials

Let ψ:[0,1]→Rψ:[0,1]→R be a strictly increasing continuous function. Let PnPn be a polynomial of degree nn determined by the biorthogonality conditions ∫01Pn(x)ψ(x)jdx=0,j=0,1,…,n−1. We study the distribution of zeros of PnPn as n→∞n→∞, and related potential theory.