List meta keys in the dashboard of custom post types

custom-dashboard-columns

// Add custom column to the Papers area
add_filter('manage_edit-[POST-TYPE]_columns', 'custom_papers_cols');
function custom_papers_cols($gallery_columns) {
  $new_columns['cb'] = '<input type="checkbox" />';

  $new_columns['id'] = __('ID');
  $new_columns['title'] = _x('Title', 'column name');
  $new_columns['papertype'] = __('Paper Type');
  $new_columns['author'] = __('University');

  $new_columns['email'] = __('Email');
  $new_columns['tags'] = __('Tags');

  $new_columns['date'] = _x('Date', 'column name');

  return $new_columns;
}
    // Add to admin_init function
add_action('manage_[POST-TYPE]_posts_custom_column', 'manage_paper_cols', 10, 2);

function manage_paper_cols($column_name, $id) {
  global $wpdb;
  switch ($column_name) {
    case 'id':
        echo $id;
            break;

    case 'papertype':
        $paperType = $wpdb->get_var("SELECT meta_value FROM $wpdb->postmeta WHERE post_id = {$id} AND meta_key = 'paper_type'");
        echo $paperType;
        break;
    default:
        break;
  } // end switch
}