<?php next_post_link('format', 'link', 'in_same_cat', 'excluded_categories'); ?>
<?php previous_post_link($format, $link, $in_same_cat = false, $excluded_categories=""); ?>
<?php next_post_link('format', 'link', 'in_same_cat', 'excluded_categories'); ?>
<?php previous_post_link($format, $link, $in_same_cat = false, $excluded_categories=""); ?>