Fourier-Bessel-type series: The fourth-order case. - W. Norrie Everitt; Clemens Markett (J. Approx. Theory, 2009)

On the differential equation for the Laguerre-Sobolev polynomials. - Clemens Markett (J. Approx. Theory, 2019)

The differential equation for Jacobi-Sobolev orthogonal polynomials with two linear perturbutions. - Clemens Markett (J. Approx. Theory, 2022)