<page_title> X.500 </page_title> <section_title> List of X.500 series standards </section_title> <table> <cell> X.520 <col_header> ITU-T number </col_header> </cell> <cell> The Directory: Selected attribute types <col_header> Title of Standard </col_header> </cell> <cell> X.521 <col_header> ITU-T number </col_header> </cell> <cell> The Directory: Selected object classes <col_header> Title of Standard </col_header> </cell> </table>
X.520 and X.521 is for attributes and object classes.