I'm trying to follow an older book written in 2011.

So, randomly picked 3.1.3 version since that's Nov 2011.

How do I switch to that version in my RVM?

Currently have Rails 4.0.0.beta1 version ...

Please don't suggest to put it in the Gemfile because there are a lot of other dependencies that will just be too troublesome to deal with, hence if I just switch, I'm assuming it means that other dependencies will be taken care of at the same time too, right?

UPDATE 

**-s-MacBook-Pro:agile **$ rails -v
Rails 4.0.0.beta1
**-s-MacBook-Pro:agile **$ gem install rails -v 3.1.3
Successfully installed rails-3.1.3
1 gem installed
**-s-MacBook-Pro:agile **$ rvm gemset create rails 313
gemset created rails    => /Users/**/.rvm/gems/ruby-1.9.3-p392@rails
gemset created 313  => /Users/**/.rvm/gems/ruby-1.9.3-p392@313
**-s-MacBook-Pro:agile **$ ruby -v
ruby 1.9.3p392 (2013-02-22 revision 39386) [x86_64-darwin10.8.0]
**-s-MacBook-Pro:agile **$ rvm 1.9.3p392-head@rails313
Unknown ruby interpreter version: '1.9.3p392'.
**-s-MacBook-Pro:agile **$

UPDATE AGAIN 

**-s-MacBook-Pro:agile **$ rvm gemset use 313
Using ruby-1.9.3-p392 with gemset 313
**-s-MacBook-Pro:agile **$ rails -v
/Library/Ruby/Site/1.8/rubygems/dependency.rb:296:in `to_specs': Could not find 'rails'     (>= 0) among 2 total gem(s) (Gem::LoadError)
from /Library/Ruby/Site/1.8/rubygems/dependency.rb:307:in `to_spec'
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_gem.rb:47:in `gem'
from /usr/bin/rails:18
**-s-MacBook-Pro:agile **$
ruby-on-rails ruby
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