4GB RAM Memory Upgrade for the Lenovo ThinkPad T420 | eBay
HD] Reinstalling the Keyboard/2nd RAM Slot on a Lenovo Thinkpad T420 T410 T400 X220 X200 Edge W - YouTube
HD] Installing RAM on a Lenovo Thinkpad T420 Guide T410 T400 - YouTube
T420] RAM Stick won't fit in slot : r/thinkpad
8GB Stick for IBM Lenovo ThinkPad T Series T420 T420i T420s T520 T520i. SO-DIMM DDR3 Non-ECC PC3-10600 1333MHz RAM Memory. Genuine A-Tech Brand. at Amazon.com