In addition to BLEU, 7 we also experiment with (1) iBLEU (Sun and Zhou, 2012) which was recently used for TS <cite>(Xu et al., 2016</cite>; and which takes into account the BLEU scores of the output against the input and against the references; (2) the Flesch-Kincaid Grade Level (FK; Kincaid et al., 1975 ), computed at the system level, which estimates the readability of the text with a lower value indicating higher 4 Examples are taken from Siddharthan (2006) .