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.
(..) that,you know,a clean colon is just one less thing to worry about. Leonard,I'm no expert here, but I believe in the context of a luncheon invitation, you might want to skip the reference to bowel movements. Oh,you're inviting me over to eat? Uh... yes. Oh,that's so nice. I'd love to. Great. (..)2007 TvShow: The Big Bang Theory Title: Pilot Season: 1 Episode 1