2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/64809This article gives a classification, up to symplectic equivalence, of singular Lagrangian foliations given by a completely integrable system of a 4-dimensional symplectic manifold, in a full neighbourhood of a singular leaf of focus-focus (=nodal) type.19 pages 4 fig. Written in june 2001. To appear in TopologySymplectic GeometryDynamical Systems37J35,37J15,37G20,53D22,53D12text