public static function add_all_citations($citations)
 {
     $types = CandelaCitation::postTypes();
     foreach ($types as $type) {
         $posts = get_posts(array('post_type' => $type, 'post_status' => 'any', 'posts_per_page' => '-1'));
         foreach ($posts as $post) {
             // Get existing citations and append new ones.
             $existing = CandelaCitation::get_citations($post->ID);
             if (!empty($existing)) {
                 $new = array_merge($existing, $citations);
             } else {
                 $new = $citations;
             }
             update_post_meta($post->ID, CANDELA_CITATION_FIELD, json_encode($new));
         }
     }
 }