  Given a differential operator T=\sum_{i=1}^k Q_i(z)d^i/dz^i where each Q_i(z)
is a polynomial define r=max_i deg(Q_i(z)-i). Assuming that r is nonnegative we
consider the following multiparameter spectral problem: for each positive
integer n find all polynomials V(z) of degree at most r such that the equation
  T(S(z))+V(z)S(z)=0 has a polynomial solution S(z) of degree n. We calculate
for any converging sequence of normalized polynomials V_j(z) the root-counting
measure of the corresponding sequence of polynomials S_j(z).
