I'm encountering this error message 'Extra content at the end of the document in XML' in my browser when displaying this XML document, what should I do to fix the problem?
<personnel>
<person id='demo'>
<firstname> Ali </firstname>
<lastname> Adam </lastname>
<title> Doc</title>
<sector> R&D </sector>
</person>
</personnel>
<personnel>
<person id='demo2'>
<firstname> Salem</firstname>
<lastname> Tarek </lastname>
<title> Dev </title>
<sector> Tech </sector>
</person>
</personnel>