http://juixe.com/techknow/index.php/2006/06/15/mixins-in-ruby/ http://www.innovationontherun.com/why-rubys-mixins-gives-rails-an-advantage-over-java-frameworks/ http://en.wikipedia.org/wiki/Mixin http://teambandb.typepad.com/soultech/2011/03/when-ruby-mixin-modules-collide.html