How to upgrade a Mac: Swap in new RAM, graphics card, hard drive and more | Macworld
Apple MacBook Pro 15" Retina 2.3GHz 8GB Ram Logic Board 2012 661-6481 - Part Haven
Adamanta 16GB (2x8GB) Apple Memory Upgrade DDR3L 1600MHz SODIMM Compatible for iMac (Mid 2011, Late 2012, Early/Late 2013, Late 2014, Mid 2015), MacBook Pro (Early/Late 2011, Mid 2012), Mac Mini : Amazon.ca: Electronics
MacBook Pro: How to remove or install memory - Apple Support
15" MacBook Pro Retina A1398 - Logic Board Mid 2014
Apple MacBook Pro with Retina Display (15-inch, 2014) review: Still the best higher-res laptop, but the competition is catching up - CNET