static function countByContent( $contentObjectID = false, $languageID = false, $status = null )
    {
        $cond = array();
        if ( $contentObjectID !== false )
        {
            $cond['contentobject_id'] = $contentObjectID;
        }
        if ( $languageID !== false )
        {
            $cond['language_id'] = $languageID;
        }
        if ( !is_null( $status ) )
        {
            $cond['status'] = $status;
        }
        return eZPersistentObject::count( self::definition(), $cond );
    }