How to install Debian GNU/Linux on HP Chromebook 14? USB boot doesn't works!

Following this guide from the debian wiki, I'm tring to install Debian on my HP Chromebook 14 (FALCO).

The problem is that, when I choose "Install" in the Debian-Installer's menu, instead of the installation process I receive again the screen stating that the OS verification has been turned off (Developer mode).

I want to install Debian Jessie on a SD, booting the Debian-Installer from a USB stick.