Although the mean (or sum) of word vectors is commonly adopted because of its simplicity (Mitchell and Lapata, 2010) , it seems that more complex approaches usually yield better performance (Cheng et al., 2018; Conneau et al., 2017; Cozma et al., 2018; Fu et al., 2018; <cite>Hill et al., 2016</cite>; Kiros et al., 2015; Torki, 2018; Zhao et al., 2015; Zhou et al., 2016 Zhou et al., , 2018 .