NEMIX RAM 16GB Kit (2x8GB Upgrade) DDR3-1600 SODIMM PC3-12800 for Apple MacBook Pro Mid 2012 / iMac Late 2012 / iMac 2013, Late 2014, Mid 2015, Mac Mini Late 2012 at Amazon.com
Apple iMac review (2012) | Engadget
iMac Intel 21.5" EMC 2544 Teardown - iFixit
Review: 21.5-inch 2012 iMac takes two steps forward, one step back | Ars Technica
Install memory in an iMac - Apple Support
How to Upgrade/Install Memory in a 21.5-inch iMac (Late 2012– Mid 2014) iMac14,1 iMac14,3 - YouTube
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)