1. NTT Communication Science Labs, Kyoto, Kyoto, Japan & Cornell University, Ithaca, NY, USA
2. NTT Communication Science Labs, Kyoto, Kyoto, Japan
3. NTT Communication Science Lab, Kyoto, Kyoto, Japan & University of California, Irvine, Irvine, CA, USA
4. Cornell University, Ithaca, NY, USA