  We give an explicit version of the Ramanujan-Petersson Conjecture for Hilbert
Modular Forms, and deduce the "Ramanujan" property for certain cubical
complexes. We reinterpret the results in terms of Communication Networks.
  The work will appear in the proceedings of a NATO conference on "Applications
of Algebraic Geometry to Coding Theory, Physics, and Computation", which took
place in Eilat, Israel, February 25 - March 1s 2001, to be published by Kluwer.
