FULLTEXT index select problem - Repeated records

There is a table has two fields as FULLTEXT index. When I perform select using MATCH it produces in sometimes multi repeated results for the same record. Why this is happned?

The following are :

Table Struture:

PHP Code:

---

CREATE TABLE `article` (
  `id` int(5) unsigned zerofill NOT NULL auto_increment,
  `typist_id` varchar(15) collate utf8_unicode_ci NOT NULL,
  `author_name` varchar(40) collate utf8_unicode_ci NOT NULL,
  `pub_date` datetime NOT NULL,
  `write_date` datetime NOT NULL,
  `title` varchar(255) collate utf8_unicode_ci NOT NULL,
  `content` text collate utf8_unicode_ci NOT NULL,
  `activity` tinyint(1) NOT NULL default '0',
  `last_editor` varchar(15) collate utf8_unicode_ci NOT NULL,
  `last_edit_date` datetime NOT NULL,
  PRIMARY KEY  (`id`),
  FULLTEXT KEY `title` (`title`,`content`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci COMMENT='Table handles articles' AUTO_INCREMENT=16 ; 


---

The query used

PHP Code:

---

SELECT id, pub_date, title, content FROM article WHERE MATCH(title,content) AGAINST('Some Search' IN BOOLEAN MODE) AND  activity = 1 ORDER BY pub_date DESC 


---

I forgot to mention that MySQL version is 4