iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
A-Tech 4GB 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
How to Upgrade/Install Memory in a 21.5-inch iMac (Late 2012– Mid 2014) iMac14,1 iMac14,3 - YouTube
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
How to Upgrade iMac RAM: 2012-2022: EveryMac.com
16GB iMac Memory for 27-inch Late 2012 to Mid 2015 Models 13,2 14,2 and 15,1 (8GBx2)
Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3L 1600MHz for Early/Mid/Late Mac Book Pro(2011- 2012), iMac(2011- 2015), Mac Mini(2011- 2012) MAC RAM at Amazon.com
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