Waiting-time distribution between avalanches and 1/f-noise: Experiments   on a three dimensional pile of rice
  This paper has been temporarily withdrawn by the author(s). There seems to have been an error in the data analysis and we are investigating the implications and trying to alleviate the problem. 
C. M. Aegerter, K. A. L\H{o}rincz, and R. J. Wijngaarden