2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/103393I review the status of the issue of the k-string tension in Yang-Mills theory. After a summary of known facts I discuss a weakly coupled four-dimensional Yang-Mills theory that supports non-Abelian strings and can, in certain aspects, serve as a toy model for QCD strings. In the second part of the talk I present original results obtained in a two-dimensional toy model which provides some evidence for the sine formula.Based on invited talks at the Workshop Understanding Confinement/Zakharov-Fest, Ringberg Castle, Tegernsee, May 16-21, Germany, and the Cracow School of Theoretical Physics, Zakopane, Poland, June 3-12, 2005. 33 pages. v2: typos corrected, acknowledgments added, minor corrections in equations in Sect. 11High Energy Physics - PhenomenologyHigh Energy Physics - LatticeHigh Energy Physics - Theorytext