Bob's nickname was “Elvis,” a 'reference to' the way he styled his hair. [=people called Bob “Elvis” because he styled his hair in the same way Elvis Presley did]
The course covers ancient history 'with' special 'reference to' the Roman Empire. [=the course is about ancient history and especially about the Roman Empire]
I have something further to add 'with reference to' [='with respect to', 'in regard to'] what was said earlier.
(..) But I was digging through these files... One of which I literally found in a spider web... And it turns out there were a bunch of references to a serbian thug, street names "the rat" and "the butcher," who's known to hang out at a storage unit (..)2013 TvShow: Brooklyn Nine-Nine Title: Pilot Season: 1 Episode 1