@UNPUBLISHED{publication1, title = "The symmetric semi-classical orthogonal polynomials of class two and some of their extensions", author = "{FILIPUK, Galina} and {REBOCHO, Maria das Neves}", year = "2018-06-22", abstract = "We study symmetric sequences of orthogonal polynomials of class two related to Stieltjes functions satisfying a Riccati type differential equation with polynomial coefficients. We show difference equations for the recurrence coefficients of the orthogonal polynomials as well as for related quantities. Some of such recurrences are identified with discrete Painlev\é equations. ", url = "http://www.mat.uc.pt/preprints/eng\_2018.html", note = "" }