Velocity distributions in vertically vibrated granular media
  This paper has been withdrawn by the authors. It has been superceded by an improved investigation: "Velocity statistics in vibrated granular media" W. Losert, D.G.W. Cooper, J. Delour, A. Kudrolli, and J.P. Gollub (submitted to Chaos for a special issue on Granular Materials) cond-mat/9901203 
J. Delour, A. Kudrolli, and J.P. Gollub