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.
(..) Sorry, are we collecting for charity, Sherlock? What? A young man's outside with crates of books. So the numbers are references. To books. To specific pages and specific words on those pages. Right, so... and , that means? (..)2010 TvShow: Sherlock Title: The Blind Banker Season: 1 Episode 2