From: Elementary ep. 4.13
Title (& tatt): “A Study in Charlotte” (victim’s tattoo is initials: RACHE, which has a double meaning)
Reference: Obviously the title of this ep is a play on the title of the first Doyle canon story, A Study in Scarlet. As a further treat, the victim (Charlotte) is German, and her tattoo of RACHE is immediately noticeable by Sherlock as German for “revenge” (Gregson even suggests it’s an incomplete “Rachel” first, just like in Doyle). In this ep, the tattoo is a touch up addition, which ends up being a major clue into whodunit. In A Study in Scarlet, RACHE is scrawled on the wall in blood by the murderer, as a blind.