iMac RAM upgrade: Here's an affordable way to improve multitasking - 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
iMac 27" 2013 SSD upgrade - IT-Tech Online
Install memory in an iMac - Apple Support
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
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
How to Upgrade the Main Drive in a 27-inch iMac (Late 2012 – 2019) - YouTube
How to upgrade the 27-inch 5K iMac (2019) with a massive 128GB of RAM [Video] - 9to5Mac
Can you upgrade the RAM in the 27-inch iMac? | iMore
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013