I've always been curious, what are the legalities of referrencing something from the real world in your story? I see it all the time in books. Characters will drive real world cars. People will drink a Coke. A scene will have a real world band playing over the radio. Gun companies' weapons will be used by the heroes. There was even one story I've read, whose introduction in a chapter was all about how cool the band Journey is before moving on. Then I read stories where they seem to go out of their way to create their own car makers, sodas, bands, Vegas strip hotels, etc. So that made me wonder if there were legalities to those referrences/descriptions? If I wanted a character in my story for, example, to listen to AC/DC before putting boot to ass would I have to seek AC/DC's permission?