1. CFR 211.67, Equipment Cleaning and Maintenance.
2. CFR 211.160 (b), Laboratory Controls.
3. FDA Guide to Inspections Validation of Cleaning Process,1998
4. EMEA Annex 15: Qualification and Validation,2015
5. FDA warning letter (WL: 320-13-07), http://www.fda.gov/iceci/enforcementactions/warningletters/ucm338048.htm.