1. Office of Rare Diseases Research (NIH) http://rarediseases.info.nih.gov/RareDiseaseList.aspx?PageID=1.
2. EMEA Health EU—Rare diseases; http://ec.europa.eu/health-eu/health_problems/rare_diseases/index_en.htm.
3. European Medicines Agency Guideline on clinical trials in small populations; www.ema.europa.eu/docs/en_GB/document_library/Scientific_guideline/2009/09/WC500003615.pdf.
4. Institute of Medicine Small Clinical Trials: Issues and Challenges C. H. Evans S. T. Ildstat Eds. (National Academy Press Washington DC 2001); http://www.nap.edu/catalog/10078.html.
5. Office of Rare Diseases Research (NIH) and Office of Orphan Products Development (FDA) The science of small clinical trials lecture series; http://videocast.nih.gov/podcasts.asp?c=88.