You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <embeddedin geicontinue="10|Stub|2650" />
  </query-continue>
  <query>
    <pages>
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      <page pageid="1324" ns="4" title="VLOS:Ưu điểm" contentmodel="wikitext" pagelanguage="vi" touched="2016-12-18T17:42:10Z" lastrevid="36561" counter="10295" length="1858" />
      <page pageid="1383" ns="0" title="Các câu nói hay liên quan đến khoa học" contentmodel="wikitext" pagelanguage="vi" touched="2017-05-20T17:11:50Z" lastrevid="15189" counter="6598" length="2520" />
      <page pageid="1474" ns="4" title="VLOS:Nguồn tài liệu khoa học" contentmodel="wikitext" pagelanguage="vi" touched="2016-12-18T17:42:10Z" lastrevid="1771" counter="3398" length="409" new="" />
      <page pageid="1483" ns="4" title="VLOS:Sách hướng dẫn/Quản lí" contentmodel="wikitext" pagelanguage="vi" touched="2016-12-18T17:42:10Z" lastrevid="17847" counter="3103" length="5234" />
      <page pageid="1484" ns="4" title="VLOS:Sách hướng dẫn/Giao lưu và thảo luận" contentmodel="wikitext" pagelanguage="vi" touched="2016-12-18T17:42:10Z" lastrevid="17849" counter="2436" length="2564" />
      <page pageid="1917" ns="0" title="Toan hoc, nguyen anh thu, lop 9, 2005" contentmodel="wikitext" pagelanguage="vi" touched="2017-05-20T17:11:45Z" lastrevid="2721" counter="5912" length="206" />
      <page pageid="2087" ns="0" title="Toán học, Đề thi toán vô địch thế giới IMO, 2000" contentmodel="wikitext" pagelanguage="vi" touched="2017-05-20T17:11:49Z" lastrevid="3285" counter="2505" length="1655" />
      <page pageid="2102" ns="0" title="Toán học, Olympic toán toàn quốc - Việt nam 2003" contentmodel="wikitext" pagelanguage="vi" touched="2017-05-20T17:11:49Z" lastrevid="3280" counter="2302" length="1613" />
    </pages>
  </query>
</api>