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.
(..) What the hell kind of a blip is that? Learned a lot. In the end though, I kind of screwed it up. I called over there for a reference, left word with some snooty girl. Next thing you know, I got a fax from Miranda Priestly herself... saying that of all the assistants she's ever had... (..)2006 The Devil Wears Prada