Targets option in Inspector is missing...

I am following the Unity Tanks tutorial for controlling the camera movement. Near the end of the tutorial it asks to drop the Tank Gameobject onto the public variable 'Targets' of the Camera Control Script, but on the dropdown menu of the Camera Control Script in Unity there is no 'Targets'. I can see from the tutorial video where it should be, but it's not there on my computer.

Please any help?