(Littell, Corcoran, & Pillai 2008) 
Introductory video from Yale University's informative video series on systematic reviews:
Systematic reviews are an integral part of Evidence Based Practice. They are types of syntheses, which sit in the middle of the 6S Pyramid of filtered or pre-appraised evidence. The 6S Pyramid shows the hierarchy of the strongest types of medical evidence.
For more information on Evidence Based Practice, please visit the EBP section of the Medicine Subject Guide: