-[[Google reCAPTCHA を使ってみる(コンタクトフォーム) | Web Design Leaves:http://www.webdesignleaves.com/wp/php/1673/]]
-[[GitHub - google/recaptcha: reCAPTCHA is a free service to protect your website from spam and abuse.:https://github.com/google/recaptcha]]
-[[Composer:https://getcomposer.org/]]
-[[PHP-FIG — PHP Framework Interop Group:http://www.php-fig.org/]]