2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53368By generalizing the Drinfel'd--Sokolov reduction we construct a large class of W algebras as reductions of Kac--Moody algebras. Furthermore we construct actions, invariant under local left and right W transformations, which are the classical covariant induced actions for W gravity. Talk presented by T. Tjin at the Trieste Summerschool on strings and related topics.8 pages, THU-92/26, ITFA-92/24High Energy Physics - Theorytext