TypeScript modules

I am wondering if it is possible somehow to have two or more classes in two or more files added to the same module in TypeScript. Something like this:

//src/gui/uielement.ts
module mylib {
    module gui {
        export interface UIElement {
            public draw() : void;
        }
    }
}

//src/gui/button.ts
///<reference path='uielement.ts'/>
module mylib {
    module gui {
        export class Button implements UIElement {
            constructor(public str : string) { }
            draw() : void { }
        }
    }
}

There will probably be dozens of GUI classes, so having them all in the same file will not be possible. And all my classes will be in the 'mylib' module. But how do I do that?

If the module mylib {...} is translated into a function then all content of all mylib blocks in all files should be contained within the same function.

Is this at all possible?

When I compile I get this:

$ tsc src/gui/button.ts 
src/gui/button.ts(4,39): The name 'UIElement' does not exist in the current scope