http://jurnal.mageric.net/index.php?option=com_content&view=article&id=51&Itemid=51 http://jurnal.mageric.net/index.php?option=com_content&view=article&id=35&Itemid=35 http://jurnal.mageric.net/index.php?option=com_content&view=article&id=326&Itemid=326