merging-xmls

i have got a fairly conplicated problem ( atleast for me :( )
i have got 3 xml files that contains university result data from 3 different
regions.and i have to merge them into one xml with all the data from 3 xmls.
The resultant XML should have the same structure as individual XMLs.
for example,
xml1:
<?xml version="1.0"?>
<university-records>
	<univ-ids>
		<univ id = "KSU">
			<name>Kansas State University</name>
			<location>Kansas<location>
		</univ>
		<univ id = "FAU">
			<name>Florida Atlantic University</name>
			<location>Florida<location>
		</univ>
		<univ id = "MSU">
			<name> Mississipi State University</name>
			<location> Mississipi <location>
		</univ>
		<univ id = "OSU">
			<name>Ohio State University</name>
			<location> Ohio <location>
		</univ>
	</univ-ids>
	<university-results>
		<university univ-id = "KSU">100%</university>
		<university univ-id = "MSU">90%</university>
		<university univ-id = "FAU">80%</university>
	</university-results>
</university-records>

xml2:
<?xml version="1.0"?>
<university-records>
	<univ-ids>
		<univ id = "OSU">
			<name> Ohio State University</name>
			<location> Ohio <location>
		</univ>
		<univ id = "WSU">
			<name> Wisconsin state University</name>
			<location> Wisconsin <location>
		</univ>
		<univ id = "RPI">
			<name> Rensellar polytechnic Institute </name>
			<location> New Jersey <location>
		</univ>
		<univ id = "MSU">
			<name> Mississipi State University</name>
			<location> Mississipi  <location>
		</univ>
	</univ-ids>
	<university-results>
		<university univ-id = "OSU">70%</university>
		<university univ-id = "WSU">100%</university>
		<university univ-id = "RPI">100%</university>
	</university-results>
</university-records>
xml3:
<?xml version="1.0"?>
<university-records>
	<univ-ids>
		<univ id = "NSU">
			<name> Newyork State University</name>
			<location> Newyork <location>
		</univ>
		<univ id = "BU">
			<name> Belmont University</name>
			<location> Belmont <location>
		</univ>
		<univ id = "WSU">
			<name>Wisconsin state University</name>
			<location> Wisconsin <location>
		</univ>
		<univ id = "BCM">
			<name> Berklee College of Music</name>
			<location> Berklee <location>
		</univ>
	</univ-ids>
	<university-results>
		<university univ-id = "NU">70%</university>
		<university univ-id = "BU">60%</university>
		<university univ-id = "BCM">100%</university>
	</university-results>
</university-records>

<university-records>
	<univ-ids>

		<univ id = "KSU">
			<name>Kansas State University</name>
			<location>Kansas<location>
		</univ>
		<univ id = "FAU">
			<name>Florida Atlantic University</name>
			<location>Florida<location>
		</univ>
		<univ id = "MSU">
			<name> Mississipi State University</name>
			<location> Mississipi <location>
		</univ>
		<univ id = "OSU">
			<name> Ohio State University</name>
			<location> Ohio <location>
		</univ>
		<univ id = "OSU">
			<name> Ohio State University</name>
			<location> Ohio <location>
		</univ>
		<univ id = "WSU">
			<name> Wisconsin state University</name>
			<location> Wisconsin <location>
		</univ>
		<univ id = "RPI">
			<name> Rensellar polytechnic Institute </name>
			<location> New Jersey <location>
		</univ>
		<univ id = "MSU">
			<name> Mississipi State University</name>
			<location> Mississipi  <location>
		</univ>
		<univ id = "NSU">
			<name> Newyork State University</name>
			<location> Newyork <location>
		</univ>
		<univ id = "BU">
			<name> Belmont University</name>
			<location> Belmont <location>
		</univ>
		<univ id = "WSU">
			<name>Wisconsin state University</name>
			<location> Wisconsin <location>
		</univ>
		<univ id = "BCM">
			<name> Berklee College of Music</name>
			<location> Berklee <location>
		</univ>

	</univ-ids>
	<university-results>
		<university univ-id = "NU">70%</university>
		<university univ-id = "BU">60%</university>
		<university univ-id = "BCM">100%</university>
		<university univ-id = "OSU">70%</university>
		<university univ-id = "WSU">100%</university>
		<university univ-id = "RPI">100%</university>
		<university univ-id = "KSU">100%</university>
		<university univ-id = "MSU">90%</university>
		<university univ-id = "FAU">80%</university>
	</university-results>
</university-records>

Things to be noticed here: The <univ-ids> in each of the xml files have some
<univ-id> elements  which are there in other xmls as well. for example the
			<univ id = "MSU">
			<name> Mississipi State University</name>
			<location> Mississipi <location>
			</univ>
which is in the xml2
similarly..
			<univ id = "OSU">
			<name> Ohio State University</name>
			<location> Ohio <location>
			</univ>
is there in both the xml files..

Thanks in advance..
laura