1. IPEC FAQs: What are Pharmaceutical Excipients? http://ipecamericas.org/about/faqs#question1
2. FDA 2004 Pharmaceutical cGMPs for the 21st Century - A Risk-Based Approach http://www.fda.gov/downloads/drugs/developmentapprovalprocess/manufacturing/questionsandanswersoncurrentgoodmanufacturingpracticescgmpfordrugs/ucm176374.pdf