The Girl Who Dreamed Only Geese

Have been looking at children's books with an eye to great illustrations of a diverse range of kids.    Love this Leo & Diane Dillon painting from "The Girl Who Dreamed Only Geese and Other Tales of the Far North".

I might need to try to get all of their books: they're amazing illustrators AND they represent a wide range of people in their art.  This particular image would make a great framed print, don't you think?  How do you go about getting permission to do that, I wonder?