Kh. Kwon et al., CHARACTERIZATION OF CLASSICAL TYPE ORTHOGONAL POLYNOMIALS, Proceedings of the American Mathematical Society, 120(2), 1994, pp. 485-493
We characterize the classical type orthogonal polynomials {P(n)(x)}0in
finity satisfying a fourth-order differential equation of type [GRAPHI
CS] where l(i)(x) are polynomials of degree less-than-or-equal-to i an
d lambda(n) is a constant. They are only the orthogonal polynomials sa
tisfying an orthogonality of the form [tau2, P(m)''P(n)'') + [tau1, P(
m)'P(n)'] + [tau0, P(m)P(n)] = 0 for m not-equal n where tau0, tau1, a
nd tau2 are moment functionals.