MacBook Pro 13" Unibody Early 2011 RAM Replacement - iFixit Repair Guide
Amazon.com: Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac(Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) MAC RAM Upgrade :
Is It Worth It to Upgrade RAM on a Macbook Pro?
MacBook Pro 13" Unibody Early 2011 RAM Replacement - iFixit Repair Guide
Apple 13" MacBook Pro 2011 2.4GHz Core i5 500GB HDD 4GB A1278 MD313LL/A +C Grade 885909531653 | eBay