iMac (27-inch, Late 2013) - Technical Specifications
8GB 2 X4GB Memory for iMac 27" inch 3.2GHz Quad Core Intel Core i5 Late 2013 ME088LL/A 1600MHz DDR3 (PC3-12800) SO-DIMMs RAM (PARTS-QUICK Brand) at Amazon.com
A-Tech 8GB Kit (2x4GB) 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
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
iMac (27-inch, Late 2013) - Technical Specifications
How to upgrade RAM iMac late 2013 21.5inch - break & fix MOVIE - YouTube
Mac RAM Upgrade, Best iMac Memory Upgrade – Best Reviews
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
Install memory in an iMac - Apple Support
Install memory in an iMac - Apple Support
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
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
Apple iMac 27" Late 2013 i7-3.5GHz/16GB RAM/256 GB SSD/ GPU GTX 775M 2GB A1419 | eBay