/usr/include/InsightToolkit/Numerics/FEM/ is in libinsighttoolkit3-dev 3.20.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/InsightToolkit/Numerics/FEM/itkFEM.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement1DStress.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement1DStress.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearLine.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearLineStress.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearQuadrilateral.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearQuadrilateralMembrane.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearQuadrilateralStrain.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearQuadrilateralStress.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearTriangular.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearTriangularMembrane.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearTriangularStrain.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0LinearTriangularStress.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0QuadraticTriangular.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0QuadraticTriangularStrain.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC0QuadraticTriangularStress.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DC1Beam.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DMembrane.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DMembrane.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DStrain.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DStrain.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DStress.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement2DStress.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DC0LinearHexahedron.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DC0LinearHexahedronMembrane.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DC0LinearHexahedronStrain.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DC0LinearTetrahedron.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DC0LinearTetrahedronMembrane.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DC0LinearTetrahedronStrain.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DMembrane.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DMembrane.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DStrain.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElement3DStrain.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElementBase.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElementStd.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElementStd.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMElements.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMException.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMGenerateMesh.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMImageMetricLoad.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMImageMetricLoad.txx
/usr/include/InsightToolkit/Numerics/FEM/itkFEMImageMetricLoadImplementation.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMInitialization.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMItpackSparseMatrix.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLightObject.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLinearSystemWrapper.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLinearSystemWrapperDenseVNL.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLinearSystemWrapperItpack.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLinearSystemWrapperVNL.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLinearSystemWrappers.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadBC.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadBCMFC.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadBase.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadEdge.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadElementBase.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadGrav.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadImplementationGenericBodyLoad.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadImplementationGenericLandmarkLoad.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadImplementationTest.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadLandmark.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadNode.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadPoint.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoadTest.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMLoads.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMMacro.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMMaterialBase.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMMaterialLinearElasticity.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMMaterials.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMObjectFactory.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMP.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMPArray.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMSolution.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMSolver.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMSolverCrankNicolson.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMSolverHyperbolic.h
/usr/include/InsightToolkit/Numerics/FEM/itkFEMUtility.h
/usr/include/InsightToolkit/Numerics/FEM/itkVisitorDispatcher.h
/usr/include/InsightToolkit/Numerics/FEM/itpack.h