Harder, better, faster, stronger: A review of the 27-inch iMac | Ars Technica
Install memory in an iMac - Apple Support
Apple Officially Confirms 21.5” iMac RAM Is Non-User-Replaceable
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Refurbished: Apple iMac 21.5-Inch "Core i5" 2.9GHz (Late 2012) A1418 MD094LL/A 8GB RAM 1TB HDD NVIDIA GT 650M MacOS MOJAVE USB Keyboard & Mouse Grade B - Newegg.com
CMS 32GB (4X8GB) DDR3 12800 1600MHz Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I7 3.4 27-Inch (Late 2012) - A6 at Amazon.com
Install memory in an iMac - Apple Support
Apple's 27" iMac Late 2012 model. How to upgrade the ram to 16GB - YouTube
NEMIX RAM 16GB Memory Upgrade Kit (2x8GB) DDR3L 1600MHz PC3L-12800 SODIMM Compatible for Apple for Mac Book Pro(Early/Mid 2012), iMac, Mac Min at Amazon.com
Apple iMac (Late 2012) review (21.5- and 27-inch) | Macworld
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
What Does It Take To Upgrade a 2012 iMac 21.5"?
Apple's 2012 iMac: Ready for its close-up (pictures) - CNET
Apple iMac 21.5" Desktop - 2.7GHz Quad-Core i5 - 8GB RAM - 1TB HDD - (2012) - Silver - Best Deal in Town
A-Tech 8GB RAM for Apple MacBook Pro (Mid 2012), iMac (Late 2012, Early/Late 2013, Late 2014, Mid 2015), Mac Mini (Late 2012) | DDR3 1600MHz SODIMM PC3-12800 204-Pin SO-DIMM Memory Upgrade at Amazon.com