Evaluation Following previous work (Woodsend and Lapata, 2011; Xu et al., 2016) we evaluated system output automatically adopting metrics widely used in the simplification literature.
we used BLEU 5 (Papineni et al., 2002) to assess the degree to which generated simplifications differed from gold standard references and the Flesch-Kincaid Grade Level index (FKGL;Kincaid et al.