I need some books that cover the Vitali Covering Theorem. Ofcourse there's wikipedia, but I need actul books that take you through the background and details of the proof (via the covering lemma ofcourse). I'm doing a project on this topic. I tried looking for the books that wikipedia lists at my universities library, but they only have the one by Natanson. Natanson's book is quite old, and only deals with subsets of the real line, whereas I need something that deals with R^n or a general metric space.
Btw, I'm still an undergrad.