Referencing a model between files
 

So, i know how do reference an object within a file, but i cant figure out how to reference a model between files. Im working on an animation with maybe 15 different shots. Im starting to block out the animation, but i only havee stand in models for the most part. I have all the models saved individually, but at the moment i can only import a copy of them into another scene. I want to just get an instance of it so when i change the first one, they all change. It must be so simple, but i just dont see it.