The paper concluded that the conditional entropy of Indus inscriptions closely matched those of linguistic systems like the Sumerian logo-syllabic system, Rig Vedic Sanskrit etc., but they are careful to stress that by itself does not imply that the script is linguistic. A follow-up study presented further evidence in terms of entropies of longer sequences of symbols beyond pairs.[30] However, Sproat claimed that there existed a number of misunderstandings in Rao et al., including a lack of discriminative power in their model, and argued that applying their model to known non-linguistic systems such as Mesopotamian deity symbols produced similar results to the Indus script. Rao et al.'s argument against Sproat's claims and Sproat's reply were published in Computational Linguistics in December 2010.[31] The June 2014 issue of Language carries a paper by Sproat that provides further evidence that the methodology of Rao et al. is flawed.[32] Rao et al.'s rebuttal of Sproat's 2014 article and Sproat's response are published in the December 2015 issue of Language.[33][34]