1. Stanford University School of Medicine, Stanford Patient Education Research Center, 1000 Welch Rd, Palo Alto, CA 94306, USA
2. Stanford University School of Medicine, Stanford Patient Education Research Center, 1000 Welch Rd, Palo Alto, CA 94306, USA,
3. Department of Health, 7E58 Quarry House, Leeds, LS2 7UE, UK
4. Department of Health, 2 Priory Road, Beauly, Inverness-shire, IV4 7GD, UK