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.
(..) He tossed and turned all night. So you slept together? He's divorced. I'm single. There's nothing enervating about it. Oh, for future reference, that word doesn't mean what you think. Look, are you aware that Dr. Elliot had a gambling problem? That was Seth's one fault. (..)2008 TvShow: Bones Title: The Finger in the Nest Season: 4 Episode 3