Recent studies have treated text simplification as a monolingual machine translation problem in which a simple synonymous sentence is generated using the framework of statistical machine translation (Specia, 2010;Zhu et al., 2010;Coster and Kauchak, 2011a;Coster and Kauchak, 2011b;Wubben et al., 2012;Štajner et al., 2015a;Štajner et al., 2015b;Goto et al., 2015).
unlike statistical machine translation, which uses bilingual parallel corpora, text simplification requires a monolingual parallel corpus for training.