2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67054We give a natural cohomological interpretation of Letzter-Makar-Limanov invariants for rings of differential operators on algebraic curves.7 pages, to appear in the Proceedings of the Workshop ``Commutative Algebra, Algebraic Geometry and Representation Theory'' (Fields Institute, Toronto, August 2002)Algebraic GeometryK-Theory and HomologyQuantum AlgebraRings and Algebrastext