Connect differential input clock with the pll

I've cheked in this file "Cyclone IV Device Family Pin Connection Guidelines" and it says :

"Dedicated global clock input pins that can also be used for the positive terminal inputs for

differential global clock input or user input pins.

In Cyclone IV GX devices, some of these pins are optional high speed differential reference clock

positive input"

, so i can use it as a input, great !! :D, thanks to everybody for help me