[Groff] Refer Usage Question

[Frank Jahnke]

I use refer a lot to process references in [gt]roff.  I have been unable
to figure out how to handle the groupings of references.  An example
would be:

The flux capacitor has been studied widely [7-23] after the pioneering
work of Smith [11-15]...

where those references are listed at the end of the document.  

It is easy to have the references listed as [7, 8, 9, and so on] after
they are cited.  Is there a way to do this without suppressing the
reference in the text body and putting it in manually?

Frank