Memory RAM Upgrade for Apple MacBook Pro 15-inch Mid 2012 4GB/8GB DDR3 SODIMM | eBay
A-Tech 8GB 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
Macbook Pro Apple 13" inch Catalina 10.15 (2012-2014 model) w/ 16GB RAM Upgrade! | eBay
Like tinkering with your MacBook Pro? Non-retina may be where it's at | Ars Technica
iFixit Launches Repair Guides for Retina MacBook Pro - MacRumors
16 GB RAM Upgrade on MacBook Pro 15" (mid 2012) NON Retina - YouTube
MacBook Pro 13" Unibody A1278 (Mid 2012) RAM Upgrade Kit