Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
21.5" iMac (2012) Teardown - YouTube
APPLE IMAC LATE 2012 27" INCH i7 3.4GHz QUAD 16GB RAM 1 TB HD | eBay
Install memory in an iMac - Apple Support
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Install memory in an iMac - Apple Support
Memory upgrade: Apple iMac 2012/2013/2014 (Howto)
A-Tech 32GB Kit (4x8GB) RAM for Apple iMac (Late 2012, Late 2013, Late 2014, Mid 2015) | DDR3 1600MHz SODIMM PC3-12800 204-Pin SO-DIMM Max Memory Upgrade at Amazon.com