2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/35886The null surface formalism of GR in three dimensions is presented, and the gauge freedom thereof, which is not just diffeomorphism, is discussed briefly.6 pages, LaTeX. To appear in Proceedings of the sixth workshop on General Relativity and GravitationGeneral Relativity and Quantum Cosmologytext