Merge two different xml files into one

[Kjetil Finsrud]

I have two xml files that I wish to join/merge into one. The first
file (sp.xml)includes information about study programmes and the
second one includes information about each course. The only thing I
want from file number two(course.xml) abouts courses is credits.
credits pr. course. I am using xsl to show the data.

Here's the first xml file(sp.xml):
<studyinfo>
<studyprogramme>
<name>Bachelor Agroecology</name>
<language>Norwegian</language>
<code>B-GEOM</code>
<studyoptions>
<coursecomposition>
<coursecombination level ="1">
<coursecombinationcode>B-GEOM-OBL</coursecombinationcode>
<coursecombinationame>Geomatikk</coursecombinationame>
<course>
<courseid>
<coursecode>STAT100</coursecode>
<institutenr>192</institutenr>
</courseid>
<coursename>Statistics</coursename>
<semester>1</semester>
<status>O</status>
--> here I want credits from the other xml file(course.xml)!
</course>
etc.
</coursecombination>
</coursecomposition>
</studyoptions>
</studyprogramme>
</studyinfo>
Here's file number two(course.xml):
<studyinfo>
<courses>
<course>
<courseid>
coursecode>STAT100</coursecode>
<institutenr>192</institutenr>
</courseid>
<coursename>Statistics</coursename>
<semester>1</semester>
<status>O</status>
<credits>10</credits> ---->I want this info into my first
file(sp.xml)
</course>
</courses>
</studyinfo>

etc.
---------------------------------

I loop through the document number one (sp.xml)and I have tried using
document() function, but only get the credits for the first course!
The credits for the rest of the courses are from the first course in
the course.xml file, therefore the same.

Also tried <xsl:copy of select="">, but with no luck yet.

Have you any suggestions on a solution for this problem?