“…For efficiency, we use heuristic functions to make a rough estimation. Specifically, we consider the linguistic features designed for readability assessment that have been demonstrated to be effective in previous studies (Feng et al, 2010;Schumacher et al, 2016), and choose the most used linguistic features that can be operated at the sentence level to build the heuristic functions. In total, eight heuristic functions h 2 {len, ans, anc, lv, art, ntr, pth, anp} corresponding to eight distinct features from three aspects are used to compute the reading score of a sentence, as shown in Table 1.…”