Chapter 2 - Form Validation (symfony 1.1 legacy version)
Symfony 2.3.6. nested form - Stack Overflow
Advanced Forms (symfony 1.4 legacy version)
Symfony Docs on Twitter: "We've just merged a massive improvement of the articles related to Symfony Form Themes (https://t.co/sgqJxioa8Z) and Form Customization (https://t.co/Ars1v2gLqj) (and we removed more than 800 lines of text