The citation to the paper by Fu and Li, 1993, given in this paper is to a very nice paper, but it is the wrong paper by Fu and Li in 1993. There was another one in that year by those authors.

The correct citation should have been to this paper: 

   Fu, Y. X. and Li, W.-H.  1993.  Estimating effective population size from 
      samples of sequences: inefficiency of pairwise and segregating sites as
      compared to phylogenetic estimates. Genetics  134: 1261-1270.