On an Application of Relative Entropy
  We describe general approach to classification of character sequences (texts, DNA) using relative entropy estimated by off-the-shelf compression and Markov Chains and find them precise enough.   We also notice that the method for estimating relative entropy described in the paper cond-mat/0108530 "Language Trees..." by D. Benedetto et al. was considered earlier and was found to be easily surpassed by the simple and computationally effective first order Markov Chain approach. 
Dmitry V. Khmelev and William J. Teahan