How to Upgrade Memory in a 27-inch iMac (Late 2012-2013) iMac13,2 and iMac14,2 - YouTube
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Upgrading an iMac — Buchanan Consulting
iMac (21.5-inch, Late 2013) - Technical Specifications
Refurbished Apple iMac 14,1/i5-4570S/16GB Ram/1TB HDD/21.5"/A (Late 2013) | SafepcDirect