2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/152097We consider formal deformations of the Poisson algebra of functions (with singularities) on $T^*M$ which are Laurent polynomials of fibers. Tn the case: $\dim M=1$ ($M=S^1, {\bf R}$), there exists a non-trivial $\star$-product on this algebra non-equivalent to the standard Moyal product.15 pages, also available via anonymous ftp at ftp://cpt.univ-mrs.fr/ or gopher://cpt.univ-mrs.fr/Differential Geometrytext