1. AT&T Labs - Research, 180 Park Avenue, Florham Park, NJ 07932, USA
2. Courant Institute of Mathematical Sciences, New York University, 719 Broadway, 12th Floor, New York, NY 10003, USA
3. Center for Spoken Language Understanding, OGI School of Science & Engineering, Oregon Health & Science University, 20000 NW Walker Road, Beaverton, Oregon 97006, USA