Review: 21.5-inch 2012 iMac takes two steps forward, one step back | Ars Technica
How to Upgrade Memory in a 27-inch iMac (Late 2012-2013) iMac13,2 and iMac14,2 - YouTube
What Does It Take To Upgrade a 2012 iMac 21.5"?
16GB Memory Upgrade Kit for 2012-2013 iMac 21.5-Inch
iMac (21.5-inch, Late 2012) - Technical Specifications
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 PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
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
Install memory in an iMac - Apple Support
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
Apple's 2012 iMac: Ready for its close-up (pictures) - CNET
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz PC3-12800 SODIMM 204-Pin Memory Upgrade at Amazon.com
Apple iMac 21.5-Inch (Late 2012) Review | PCMag
Install memory in an iMac - Apple Support
Apple 21.5" Pre-Owned iMac Desktop Intel Core i5 2.7GHz 8GB Memory 1TB HDD (2012) Silver MD093LL/A - Best Buy