Links:
- https://www.youtube.com/channel/UCxVjMma0fnJmn0TMILjcEfg
- http://www.slideshare.net/guilhermeblanco/object-calisthenics-applied-to-php
- http://books.google.com.br/books/about/Domain_Driven_Design.html?id=hHBf4YxMnWMC&redir_esc=y
- http://books.google.com.br/books?id=6oHuKQe3TjQC&printsec=frontcover&dq=design+patterns+gof&hl=en&sa=X&ei=e3DBU9_FMNDJsQT2jIDIBg&ved=0CCIQ6AEwAQ#v=onepage&q&f=false