How to create a module of modules

 I had heard several times that one of the new features available when DNG was created was that since modules are made of artifacts and that modules were artifacts, it was possible to import a module (containing textual artifacts) into a larger module.  I had not had a reason to use this knowledge, but recently we found a use.  We created several modules that are "sections" of the larger module - but cannot combine them into a single master document.