Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
Review: 21.5-inch 2012 iMac takes two steps forward, one step back | Ars Technica
Install memory in an iMac - Apple Support
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
Install memory in an iMac - Apple Support
Apple iMac 21.5" 2.7GHz i5 1TB HDD 8GB RAM 2012 MD093LL/A - A Grade Refurbished | Groupon
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