1. Frequency and circumstances of placebo use in clinical practice—a systematic review of empirical studies;M Fässler,2010
2. Widespread use of pure and impure placebo interventions by GPs in Germany;K Meissner,2012
3. Prescribing “placebo treatments”:results of national survey of US internists and rheumatologists;JC Tilburt,2008
4. Placebo use in the United kingdom: results from a national survey of primary care practitioners;J Howick,2013
5. A bitter pill to swallow: placebo therapy in general practice;J Comaroff,1976