Hi; I'm Juan Díaz, coauthor of the paper. With the convention used; the factor (1-x)^b has been considered as part of the integral measure and, as a consequence, not included on the weight. Along the whole code, the weight functions and measures only appear in the definition of the steady states. In the Jacobi--Piñeiro one, it can be checked that such factor (1-x)^b is actually there.
