Install memory in an iMac | Imac, Ram upgrade, Installation
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 Upgrades for iMac 21.5-Inch 2012 - Late 2013
Install memory in an iMac - Apple Support
OWC Announces Memory Upgrades From 8GB to 32GB For 2012 27" Apple iMac
New 21-Inch iMac Won't Let Users Upgrade RAM Themselves, But 27-Inch iMac Will | Cult of Mac
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 SODIMM PC3-12800 204-Pin SO-DIMM Max Memory Upgrade at Amazon.com
Memory upgrade: Apple iMac 2012/2013/2014 (Howto)
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)