/usr/include/linbox/matrix/ is in liblinbox-dev 1.4.2-5build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/linbox/matrix/abnormal-helpers.h
/usr/include/linbox/matrix/abnormal-matrix.h
/usr/include/linbox/matrix/archetype.h
/usr/include/linbox/matrix/dense-matrix.h
/usr/include/linbox/matrix/densematrix/
/usr/include/linbox/matrix/densematrix/blas-matrix-multimod.h
/usr/include/linbox/matrix/densematrix/blas-matrix.h
/usr/include/linbox/matrix/densematrix/blas-matrix.inl
/usr/include/linbox/matrix/densematrix/blas-submatrix.inl
/usr/include/linbox/matrix/densematrix/blas-transposed-matrix.h
/usr/include/linbox/matrix/densematrix/blas-triangularmatrix.inl
/usr/include/linbox/matrix/factorized-matrix.h
/usr/include/linbox/matrix/factorized-matrix.inl
/usr/include/linbox/matrix/matrix-category.h
/usr/include/linbox/matrix/matrix-domain.h
/usr/include/linbox/matrix/matrix-traits.h
/usr/include/linbox/matrix/matrixdomain/
/usr/include/linbox/matrix/matrixdomain/apply-domain.h
/usr/include/linbox/matrix/matrixdomain/blas-matrix-domain.h
/usr/include/linbox/matrix/matrixdomain/blas-matrix-domain.inl
/usr/include/linbox/matrix/matrixdomain/matrix-domain-gf2.h
/usr/include/linbox/matrix/matrixdomain/matrix-domain.h
/usr/include/linbox/matrix/matrixdomain/matrix-domain.inl
/usr/include/linbox/matrix/matrixdomain/opencl-domain-factory.h
/usr/include/linbox/matrix/matrixdomain/opencl-domain-memory.inl
/usr/include/linbox/matrix/matrixdomain/opencl-domain-util.inl
/usr/include/linbox/matrix/matrixdomain/opencl-domain.h
/usr/include/linbox/matrix/matrixdomain/opencl-domain.inl
/usr/include/linbox/matrix/matrixdomain/plain-domain.h
/usr/include/linbox/matrix/permutation-matrix.h
/usr/include/linbox/matrix/permutation-matrix.inl
/usr/include/linbox/matrix/plain-matrix.h
/usr/include/linbox/matrix/polynomial-matrix.h
/usr/include/linbox/matrix/random-matrix.h
/usr/include/linbox/matrix/random-matrix.inl
/usr/include/linbox/matrix/sliced3/
/usr/include/linbox/matrix/sliced3.h
/usr/include/linbox/matrix/sliced3/dense-matrix.h
/usr/include/linbox/matrix/sliced3/dense-sliced.h
/usr/include/linbox/matrix/sliced3/dense-sliced.inl
/usr/include/linbox/matrix/sliced3/sliced-domain.h
/usr/include/linbox/matrix/sliced3/sliced-stepper.h
/usr/include/linbox/matrix/sliced3/submat-iterator.h
/usr/include/linbox/matrix/sparse-formats.h
/usr/include/linbox/matrix/sparse-matrix.h
/usr/include/linbox/matrix/sparsematrix/
/usr/include/linbox/matrix/sparsematrix/read-write-sparse.h
/usr/include/linbox/matrix/sparsematrix/read-write-sparse.inl
/usr/include/linbox/matrix/sparsematrix/sparse-associative-vector.h
/usr/include/linbox/matrix/sparsematrix/sparse-associative-vector.inl
/usr/include/linbox/matrix/sparsematrix/sparse-coo-implicit-matrix.h
/usr/include/linbox/matrix/sparsematrix/sparse-coo-matrix.h
/usr/include/linbox/matrix/sparsematrix/sparse-csr-matrix.h
/usr/include/linbox/matrix/sparsematrix/sparse-domain.h
/usr/include/linbox/matrix/sparsematrix/sparse-ell-matrix.h
/usr/include/linbox/matrix/sparsematrix/sparse-ellr-matrix.h
/usr/include/linbox/matrix/sparsematrix/sparse-generic.h
/usr/include/linbox/matrix/sparsematrix/sparse-generic.inl
/usr/include/linbox/matrix/sparsematrix/sparse-hyb-matrix.h
/usr/include/linbox/matrix/sparsematrix/sparse-parallel-vector.h
/usr/include/linbox/matrix/sparsematrix/sparse-parallel-vector.inl
/usr/include/linbox/matrix/sparsematrix/sparse-sequence-vector.h
/usr/include/linbox/matrix/sparsematrix/sparse-sequence-vector.inl
/usr/include/linbox/matrix/sparsematrix/sparse-tpl-matrix-omp.h
/usr/include/linbox/matrix/sparsematrix/sparse-tpl-matrix-omp.inl
/usr/include/linbox/matrix/sparsematrix/sparse-tpl-matrix.h
/usr/include/linbox/matrix/sparsematrix/sparse-tpl-matrix.inl
/usr/include/linbox/matrix/sparsematrix/triples-coord.h
/usr/include/linbox/matrix/transpose-matrix.h