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.
(..) which is an inward force generated by the glass acting on the olive... Excuse me. If you were riding on the olive, you'd be in a non - inertial reference frame and would... are you okay? Yeah,I'm okay. Did you spill ketchup? - No. - I'm not okay. (..)2007 TvShow: The Big Bang Theory Title: The Fuzzy Boots Corollary Season: 1 Episode 3