+<para>
+Some tools (e.g. <systemitem role="package">po4a</systemitem>, <systemitem
+role="package">poxml</systemitem>, or the <systemitem
+role="package">translate-toolkit</systemitem>) are specialized in extracting
+the translatable material from different formats. They produce PO files, a
+format quite common to translators, which permits to see what needs to be
+retranslated when the translated document is updated.
+</para>