Entropy, a complete metric invariant for automorphisms of the torus.

@article{Adler1967EntropyAC,
  title={Entropy, a complete metric invariant for automorphisms of the torus.},
  author={R L Adler and B F Weiss},
  journal={Proceedings of the National Academy of Sciences of the United States of America},
  year={1967},
  volume={57 6},
  pages={1573-6}
}