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)