+filter.epub: filter-epub.xml
+ rm -rf book-filter
+ mkdir book-filter
+ xsltproc -o book-filter/ $(EPUB_DOCBOOK) filter-epub.xml
+ echo "application/epub+zip" > book-filter/mimetype
+ ( cd book-filter; zip -XqD ../filter.epub mimetype )
+ ( cd book-filter; zip -Xr9D ../filter.epub META-INF OEBPS )
+