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.
(..) DRAMATIC CLASSICAL MUSIC) I don't really get that shirt. HAZEL: Mmm. But Van Houten will get it. There are, like, fifty Magritte references in An Imperial Affliction. "This is not a pipe." But it is a pipe. But it's not. It is a drawing of a pipe. See? (..)2014 The Fault in Our Stars