Robust grammar-based language modeling is a topic that has received a fair bit of attention over the past decade (Chelba and Jelinek 2000; <cite>Charniak 2001</cite>; Roark 2001; Wang, Stolcke, and Harper 2004, among others) , and while this line of research has not focused on the use of manually built, narrow-domain feature grammars, there is enough similarity between the approach described in this book and the cited papers that the papers would seem to be better comparison points than the class-based language models that are chosen to represent robust approaches in the comparison.