I have the following piece of XML:

<research>
  <research.record>
    <research.record_number>1</research.record_number>
    <research.type>
      <value lang="en-US">some research type</value>
    </research.type>
    <research.type>
      <value lang="en-US">some other type of research</value>
    </research.type>
    <project.record>
      <priref>101</priref>
      <project.type>
        <value lang="en-US">some type of project</value>
      </project.type>
    </project.record>
  </research.record>
</research>
<research>
  <research.record>
    <research.record_number>2</research.record_number>
    <research.type>
      <value lang="en-US">some other type of research</value>
    </research.type>
    <research.type>
      <value lang="en-US">a third type of research</value>
    </research.type>
    <project.record>
      <priref>101</priref>
      <project.type>
        <value lang="en-US">some type of project</value>
      </project.type>
    </project.record>
  </research.record>
</research>
<research>
  <research.record>
    <research.record_number>3</research.record_number>
    <research.type>
      <value lang="en-US">some other type of research</value>
    </research.type>
    <research.type>
      <value lang="en-US">a fourth type</value>
    </research.type>
    <project.record>
      <priref>201</priref>
      <project.type>
        <value lang="en-US">some other type of project</value>
      </project.type>
    </project.record>
  </research.record>
</research>
<research>
   ... etc ...

With XSLT 1.0 I transform this XML into a list of unique project records by using xsl:key.

So far, so good...

The problem is: I also want to show unique research types for each unique project record.

My wanted output would be:

project.record 101: some research type, some other type of research, a third type of    research

project.record 201: some other type of research, a fourth type

Hope someone can help me out with the right XSLT/XPATH. (Can only use XSLT1.0)