xpath finding duplicates

[Timo Nentwig]

Hi!

<node>
<name>foo</name>
<id>1</id>
<age>7</age>
</node>
<node.....>
<node>
<name>foo</name>
<id>10</id>
<age>100</age>
</node>
<node.....>
<node>
<name>bar</name>
<id>123</id>
<age>5</age>
</node>
<node.....>
<node>
<name>bar</name>
<id>321</id>
<age>10</age>
</node>

I try to write an xpath expression that does select duplicates (the foo's
and bar's in above's example) and also add a condition which (not) to
select (the age tag above).

Well, I have failed so far

Timo