1. On semiclassical linear functionals: The symmetric companion;Arvesú;Comm. Anal. Theory Contin. Fractions,2002
2. J. Blankenagel, Anwendungen adjungierter Polynomoperatoren, Doctoral dissertation, Universitat zu Köln, 1971 (in German)
3. Note sur une nouvelle formule du calcul différentiel;Faà di Bruno;Quart. J. Math.,1855
4. Continuous symmetric Sobolev inner products;Bueno;Internat. Math. J.,2003
5. M.I. Bueno, F. Marcellán, Polynomial perturbations of bilinear functionals and Hessenberg matrices, preprint