1. Lettich M.,Insulation Outlook Magazine, Nov 2005 Issue (2005)
2. Paul Virmani Y.,National Tech Information Service, Pub. No. FHWA-RD-01-156. (2002)
3. European Federation of Insulation Contractors, FESI Document09, (2010)
4. Twomey M., American Society for Nondestructive Testing, Inc. (2007)