1. ^{{cite book|author=Active Interest Media, Inc.|title=Old-House Journal|url=https://books.google.com/books?id=s0kMqoiOhugC&pg=PA39|accessdate=25 September 2012|date=April 1977|publisher=Active Interest Media, Inc.|page=39|issn=0094-0178}}
2. ^{{cite book|author1=Philippe Boch|author2=Jean-Claude Nièpce|title=Ceramic Materials: Processes, Properties, and Applications|url=https://books.google.com/books?id=lnN1rcr4unoC&pg=PA117|accessdate=25 September 2012|date=5 January 2010|publisher=John Wiley & Sons|isbn=978-0-470-39454-0|page=117}}
3. ^{{cite book|author=William L. Ventolo|title=Your Home Inspection Guide|url=https://books.google.com/books?id=2edigWaeGPUC&pg=PA126|accessdate=25 September 2012|date=1 May 1995|publisher=Dearborn Trade Publishing|isbn=978-0-7931-1336-1|page=126}}