install - Installing and Upgrading Ram on a mid 2011 iMac (different size RAM) - Ask Different
Apple iMac 27" i5 2.7 (Mid 2011) - Technical data and benchmarks
Memory Upgrades for Apple iMac 2011 Up to 32GB
How to Upgrade Memory in a 21.5-inch or 27-inch iMac (Mid 2010) - YouTube
Apple iMac 2.5Ghz i5-2400S (Mid-2011) *No HDD/RAM* – MSU Surplus Store
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
A-Tech 32GB (4x8GB) RAM for Apple iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
Install memory in an iMac - Apple Support
A-Tech 8GB RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch), Mac Mini (Mid 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Module at Amazon.com
32.0GB OWC Memory Upgrade Kit For 2010-2011 Apple iMac