/usr/include/libgsf-1/gsf/ is in libgsf-1-dev 1.14.27-2ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libgsf-1/gsf/gsf-blob.h
/usr/include/libgsf-1/gsf/gsf-clip-data.h
/usr/include/libgsf-1/gsf/gsf-doc-meta-data.h
/usr/include/libgsf-1/gsf/gsf-docprop-vector.h
/usr/include/libgsf-1/gsf/gsf-fwd.h
/usr/include/libgsf-1/gsf/gsf-impl-utils.h
/usr/include/libgsf-1/gsf/gsf-infile-impl.h
/usr/include/libgsf-1/gsf/gsf-infile-msole.h
/usr/include/libgsf-1/gsf/gsf-infile-msvba.h
/usr/include/libgsf-1/gsf/gsf-infile-stdio.h
/usr/include/libgsf-1/gsf/gsf-infile-tar.h
/usr/include/libgsf-1/gsf/gsf-infile-zip.h
/usr/include/libgsf-1/gsf/gsf-infile.h
/usr/include/libgsf-1/gsf/gsf-input-bzip.h
/usr/include/libgsf-1/gsf/gsf-input-gio.h
/usr/include/libgsf-1/gsf/gsf-input-gzip.h
/usr/include/libgsf-1/gsf/gsf-input-http.h
/usr/include/libgsf-1/gsf/gsf-input-impl.h
/usr/include/libgsf-1/gsf/gsf-input-iochannel.h
/usr/include/libgsf-1/gsf/gsf-input-memory.h
/usr/include/libgsf-1/gsf/gsf-input-proxy.h
/usr/include/libgsf-1/gsf/gsf-input-stdio.h
/usr/include/libgsf-1/gsf/gsf-input-textline.h
/usr/include/libgsf-1/gsf/gsf-input.h
/usr/include/libgsf-1/gsf/gsf-libxml.h
/usr/include/libgsf-1/gsf/gsf-meta-names.h
/usr/include/libgsf-1/gsf/gsf-msole-utils.h
/usr/include/libgsf-1/gsf/gsf-open-pkg-utils.h
/usr/include/libgsf-1/gsf/gsf-opendoc-utils.h
/usr/include/libgsf-1/gsf/gsf-outfile-impl.h
/usr/include/libgsf-1/gsf/gsf-outfile-msole.h
/usr/include/libgsf-1/gsf/gsf-outfile-stdio.h
/usr/include/libgsf-1/gsf/gsf-outfile-zip.h
/usr/include/libgsf-1/gsf/gsf-outfile.h
/usr/include/libgsf-1/gsf/gsf-output-bzip.h
/usr/include/libgsf-1/gsf/gsf-output-csv.h
/usr/include/libgsf-1/gsf/gsf-output-gio.h
/usr/include/libgsf-1/gsf/gsf-output-gzip.h
/usr/include/libgsf-1/gsf/gsf-output-iconv.h
/usr/include/libgsf-1/gsf/gsf-output-impl.h
/usr/include/libgsf-1/gsf/gsf-output-iochannel.h
/usr/include/libgsf-1/gsf/gsf-output-memory.h
/usr/include/libgsf-1/gsf/gsf-output-stdio.h
/usr/include/libgsf-1/gsf/gsf-output.h
/usr/include/libgsf-1/gsf/gsf-shared-memory.h
/usr/include/libgsf-1/gsf/gsf-structured-blob.h
/usr/include/libgsf-1/gsf/gsf-timestamp.h
/usr/include/libgsf-1/gsf/gsf-utils.h
/usr/include/libgsf-1/gsf/gsf.h