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.
(..) Well, there's just one convict left. Whoever finds him wins. Yeah. I guess you could say he's... the Golden Snitch. Wait. Was that a "Harry Potter" reference? It most definitely was. I started reading them - 'cause you love them so much. - And? You were right. They're incredible. (..)2017 TvShow: Brooklyn Nine-Nine Title: #DUPE# Season: 4 Episode 11