http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CFkQFjAE&url=http://vmg.pp.ua/books/%25D0%259A%25D0%25BE%25D0%25BF%25D1%258C%25D1%258E%25D1%2582%25D0%25B5%25D1%2580%25D1%258B%25D0%2598%25D1%2581%25D0%25B5%25D1%2582%25D0%25B8/web/ruby%2520on%2520rails/Manning.Rails.3.in.Action.Sep.2011.pdf&ei=CLzFT66UF4vU2QWX3qTTAQ&usg=AFQjCNFVKU70nI3QGX9cVSs9SjvfjsYs2Q&sig2=tv2mOuLqSXnGDohndz3EBw