@article{MZ_1964__86_170355,
     author = {H.L. Krall and I.M. Sheffer},
     title = {On pairs of related orthogonal polynomial sets.},
     journal = {Mathematische Zeitschrift},
     pages = {425--450},
     publisher = {mathdoc},
     volume = {86},
     year = {1964},
     zbl = {0128.29402},
     url = {http://geodesic.mathdoc.fr/item/MZ_1964__86_170355/}
}