1. MIT Sloan School of Management, 100 Main St., Cambridge, MA 02142, USA.
2. Harmony Labs, 311 W 43rd St., New York, NY 10036, USA.
3. Microsoft Research New England, 1 Memorial Dr., Cambridge, MA 02142, USA.
4. Microsoft Research New York, 641 Avenue of the Americas, 7th Floor, New York, NY 10011, USA.
5. University of Pennsylvania, 3401 Walnut St., 459C, Philadelphia, PA 19104, USA.