Practical Linguistic Steganography using Contextual Synonym Substitution and a Novel Vertex Coding Method Ching-Yun Chang author Stephen Clark author 2014-06 text journal article Computational Linguistics continuing MIT Press Cambridge, MA periodical academic journal chang-clark-2014-practical 10.1162/COLI_a_00176 https://aclanthology.org/J14-2006/ 2014-06 40 2 403 448