Sony Xperia SP model not listed in 'developer.sonymobile.com/unlockbootloader' for bootloader unlocking

I don't know how I can unlock my Xperia SP phone, because the model is not listed in the site http://developer.sonymobile.com/unlockbootloader so I couldn't continue. My logic says there might be some model that is similar to this model (Xperia SP), but I don't know what model. Do you know? Any suggestions **APPRECIATED :)**