how to merge\combine BI Pub reports in one report

Hello everyone- I am trying to combine \ merge reportes created by BI Pubsher -- 11g into one report. The individual reports as you know can be created in PDF , Excel and HTML. In the Data Model I can create different datasets. However there is no possible key field I can use to combine these tables. On report level I was not able to open a report and use in the Layout two Data Models (each eblongs to a different report).

So is there a way after creating say for example 4 reports to combine \ merge them into one report.