8GB 2 X 4GB Memory for HP ProBook 4520s DDR3 PC3-10600 SODIMM RAM (PARTS-QUICK Brand) at Amazon.com
HP Probook 4520s 15.6" Windows 10 Intel i5-M450 2.4GHz 6GB RAM 250SSD | eBay
Arch Memory 4GB 204-Pin DDR3 1066 MHz So-dimm RAM for HP ProBook 4520s at Amazon.com
HP PROBOOK 4520S - Core I3 - Sous Windows 10 - Ram 4 Go - N°032050 - GRADE B
HP ProBook 4520s Intel Core i3 M380 CPU @ 2.53GHz, 4GB RAM, 320GB HDD with Microsoft Windows 10 Professional and Microsoft Office 2010 Home & Business.
HP ProBook 4520s SSD and Ram Upgrade 2021 - YouTube