Is there a way to upgrade the RAM in an early 2015 MacBook Pro without voiding the warranty? - Quora
Late-2013 15-Inch Retina MacBook Pro Review: Apple's High-Performance Notebook Tops The Field | TechCrunch
Apple MacBook Pro 15" - Core i7 2.7GHz, 16GB RAM, 512GB SSD: Amazon.de: Computer & Accessories
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 (Retina, 13-inch, Late 2013) - Technical Specifications
A-Tech 8GB Kit (2x4GB) PC3-12800 DDR3 1600MHz SODIMM Memory ram Upgrade for Apple MacBook
Apple MacBook Pro with Retina Display (13-inch, 2013) review: Not a Retina MacBook Air, but awfully close - CNET
MacBook Pro Retina 15-inch Late 2013 A1398 16GB RAM 1TB SSD | eBay
Apple Macbook Pro Retina Late 2013 15" - ME874LL/A - MacBookPro11,3 - A1398 - 2745