‘If you’ve heard it, you can say it’ - Towards an Account of Expressibility David D McDonald author Charlie Greenbacker author 2010-07 text Proceedings of the 6th International Natural Language Generation Conference John Kelleher editor Brian Mac Namee editor Ielka van der Sluis editor Association for Computational Linguistics conference publication mcdonald-greenbacker-2010-youve https://aclanthology.org/W10-4220/ 2010-07