Another new feature I've just added to #citum is compound citations that I guess are common in chemistry.

https://docs.citum.org/examples.html#compound-numeric-sets

This is feature requested for CSL awhile back that we had no idea how to implement, and in retrospect would have been impossible given the dependence on processor behavior.

https://github.com/citation-style-language/schema/issues/437

Looking for a clean solution, this is another case where I drew inspiration from #biblatex.