Resizing images with GraphicsMagick

Hello.

I recently installed GraphicsMagick ( http://GraphicsMagick.org ) and although I have figured out how to convert images, I haven't figured out how to resize them.

Here is how I convert a GIF image to a JPG image:
         gm convert image.gif image.jpg

I want to resize large.jpg (1000 px by 500 px) to small.jpg (100 px by 50 px)

How can I do that?

Thanks!