wilcoxon_signed_rank_interval = function( data, c, debugging=FALSE ){
  #
  # Returns:
  # 
  # See Page 616 from the book Probability and Statistics: For Engineering and the Sciences by Jay L. Devore
  #
  # Written by:
  # -- 
  # John L. Weatherwax                2009-04-21
  # 
  # email: wax@alum.mit.edu
  # 
  # Please send comments and especially bug reports to the
  # above email address.
  #
  #-----

  data_outer = outer( data, data, FUN="+" )
  inds = upper.tri( data_outer, diag=TRUE ) 
  data_outer = as.vector( data_outer[inds] )/2
  data_outer_sorted = sort( as.vector(data_outer) )
  if( debugging ){ print( data_outer_sorted ) }
  n = length(data)

  # Find the two ranks of the lower and upper limits:  
  ll_index = as.integer( n*(n+1)/2 - c + 1 )
  ul_index = as.integer( c ) 
  if( debugging ){
    print( c(ll_index,ul_index) ) 
  }

  list( ll=data_outer_sorted[ll_index], ul=data_outer_sorted[ul_index] )

}