David R. Traum Carl F. Andersen Waiyian Chong Darsana P. Josyula Yoshi Okamoto Khemdut Purang Michael O'Donovan-Anderson Donald Perlis Representations of Dialogue State for Domain and Task Independent Meta-Dialogue. 125-152 1999 3 Electron. Trans. Artif. Intell. D http://www.ep.liu.se/ej/etai/1999/020/ db/journals/etai/etai3.html#TraumACJOPOP99