Apple iMac 21.5” SSD Upgrade (2013-2015) HDD To Solid State Drive (SATA) | Step By Step - YouTube
REVEALED: Reg trails claw along Apple's 'austerity' 21.5-inch iMac • The Register
How do I upgrade my mid 2014 21.5 iMac? - iMac Intel 21.5" EMC 2805 - iFixit
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
2012 21.5-Inch Apple iMac Review: Slim, Sleek, And Stylish, But Far From Shallow | TechCrunch
iMac with Retina 5K Display 2014/2015 Memory Upgrades
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET