MacBook Pro 13" Retina Display Late 2013 Teardown - iFixit
SOLVED: Can RAM be upgraded? - MacBook Pro 13" Retina Display Mid 2014 - iFixit
macbook pro - Can I upgrade RAM on late 2013 retina Mac Book Pro? - Ask Different
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com