2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/59376A new classification theorem for links by the authors and Roger Fenn leads to computable link invariants. As an illustration we distinguish the left and right trefoils and recover the result of Carter et al that the 2-twist-spun trefoil is not isotopic to its orientation reverse. We sketch the proof the classification theorem. Full details will appear elsewhere15 pages, 7 figures. The paper depends on a Maple worksheet (trefoil.ms) which uses two Maple input files (normform and homology). These files are included in the "source" package. Version 2: the underlying classification theorem has been added with a sketch of proof, and the title changed accordinglyGeometric Topology57Q45, 57M25, 57M27text