2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/66590We construct anisotropic conductivities with the same Dirichlet-to-Neumann map as a homogeneous isotropic conductivity. These conductivities are singular close to a surface inside the body.Alternative proof of Prop. 1 and minor changes. To appear in Math. Res. LettersAnalysis of PDEsSpectral Theorytext