Reference author: Natural Canada

Canada, N. R. (2007). Improving Window Energy Efficiency, Why Should I Worry About my Windows?. Retrieved from www.oee.nrcan.gc.ca/residential/personal/window-efficiency.cfm?attr=4$\#$a

Canada, N. R. (2009). Repairing or Improving Existing Windows or Doors: 1- Assess the Situation, 2- Caulking, 3-Replacing Weatherstripping and Storm Windows.