Sub-lists are similar to subscribing one list to another, but w/o the
"duplicates" if you are subscribed to both lists.

Only a listserv maintainer may add the list definition keyword to your list.

I think I responded [on-list] within the last month to a related question.

For the department to which I belong, we actually have a structure:

division list which sub-lists to multiple department lists
     department lists which sub-list to multiple work-groups