Sub plan on p-adic numbers:

[Liu]

I have met p-adic numbers once, when I was learning the Banach-Tarski
theorem. I read this post at The Secret Blogging seminor, namely “That
trick where you embed the free group into a Lie group”, where p-adic
numbers are used as examples：

http://sbseminar.wordpress.com/2007/09/17/that-trick-where-you-embed-the-free-group-into-a-lie-group/

It seems to me p-adic numbers and p-adic analysis always provide with
good examples. A book written by Neal Koblitz (GTM 58) seems to be a
good introduction to this field. I will read the first chapter of it
(only twenty pages).