MacBook Pro: How to remove or install memory - Apple Support
16 GB RAM Upgrade on MacBook Pro 15" (mid 2012) NON Retina - YouTube
CMS 16GB (2X8GB) DDR3 12800 1600MHz Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® MacBook Pro Core I5 2.5 13" Mid-2012 - A7 at Amazon.com
So I assembled a Specced Out Unibody MacBook Pro 15-inch (mid-2012, 2.6GHz Core i7, 16GB 1600MHz DDR3 RAM) and installed some gradient colored backlight keyboard on it… : r/mac
MacBook Pro 15" Retina Display Mid 2012 Teardown - iFixit
MacBook Pro 15" Retina Display Mid 2012 Teardown - iFixit
Memory RAM Upgrades for MacBook Pro (2012 - Late 2016)