Voice-IF: a mixed-initiative spoken dialogue system for AT&t conference services. - Mazin G. Rahim; Giuseppe Di Fabbrizio; Candace A. Kamm; Marilyn A. Walker; A. Pokrovsky; P. Ruscitti; Esther Levin; Sungbok Lee; Ann K. Syrdal; K. Schlosser (INTERSPEECH, 2001)