2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/53385We discuss the non--perturbative formulation for $c \leq 1$ string theory. The field theory like formulation of topological and non--topological models is presented. The integral representation for arbitrary $(p,q)$ solutions is derived which explicitly obeys $p-q$ duality of these theories. The exact solutions to string equation and various examples are also discussed.15 pp, preprint FIAN/TD-15/92, latexHigh Energy Physics - Theorytext