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
Upgrade RAM on Apple Retina iMac 5K (Late 2015) / How To install memory - YouTube
Memory upgrade: Apple iMac 2012/2013/2014 (Howto)
Install memory in an iMac - Apple Support
Apple Officially Confirms 21.5” iMac RAM Is Non-User-Replaceable
2013 iMac teardowns reveal SSD slots, soldered-in CPU in the 21.5” model | Ars Technica
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
How to Upgrade RAM on MacBook Pro, iMac & More | AVG
CMS 16GB (2X8GB) DDR3 12800 1600MHz Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core I5 3.4 27-Inch (Late 2013) Me089Ll/A - A7 at Amazon.com
upgrade advice for a late 2013 27-inch iMac | MacRumors Forums