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8GB 2X4GB Memory RAM for HP ProBook 4720s 204pin 1333MHz PC3-10600 DDR3 SO-DIMM Black Diamond Memory Module Upgrade System Specific Memory - Newegg.com
CMS 8GB (2X4GB) DDR3 10600 1333MHZ NON ECC SODIMM Memory Ram Upgrade Compatible with HP/Compaq® Probook 4720S, 4520S Notebook - A29 System Specific Memory - Newegg.com
RAM and HDD upgrade on a HP ProBook 4720s - YouTube
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