1. University of California, San Francisco, and Medical Effectiveness Research Center for Diverse Populations, San Francisco, CA, USA, Tel.: +1 415 353 7931; Fax: +1 415 353 7932;
2. University of California San Francisco and San Francisco Veteran Affairs Medical Center, 4150 Clement Street, VA Medical Center, Section 111A1, San Francisco, CA 94121, USA, Tel.: +1 415 750 2093; Fax: +1 415 386 4044;