1. Information Sciences Institute, University of Southern California, Marina del Rey, CA, USA
2. Department of Computer Science, University of Southern California, Los Angeles, CA, USA. souratih@isi.edu
3. Department of Computer Science, Vrije Universiteit Amsterdam, Netherlands. f.ilievski@vu.nl
4. Computational Linguistics & Text Mining Lab, Vrije Universiteit Amsterdam, Netherlands. pia.sommerauer@vu.nl
5. Department of Computer Science, University of Southern California, Los Angeles, CA, USA. yifjia@isi.edu