Tugkan Batu Sanjoy Dasgupta Ravi Kumar Ronitt Rubinfeld The Complexity of Approximating the Entropy. 132-150 2005 35 SIAM J. Comput. 1 http://epubs.siam.org/SICOMP/volume-35/art_40364.html db/journals/siamcomp/siamcomp35.html#BatuDKR05