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.
(..) - I said Batman was gay. Sheesh. You ask one lady if she's Tyler Perry in drag... and suddenly, you're the bad guy. It's a reference. That's my humor. - Abed gets it. - Oh, you're all hiding out in here. - Yeah. You know us, hide away. - "Hiding"? Well, be careful. (..)2013 TvShow: Community Title: Cooperative Escapism in Familial Relations Season: 4 Episode 5