HP Elitebook 840 G1 RAM Replacement - iFixit Repair Guide
StoneTaskin 802523-601 802523-001 for HP EliteBook 840 G1 Motherboard Upgrade I3 I5 6050A2560201-MB-A03 UMA w i7-4500U CPU MB - AliExpress
A-Tech 4GB Module for HP EliteBook 840 G1 Laptop & Notebook Compatible DDR3/DDR3L PC3-12800 1600Mhz Memory Ram (ATMS266381B12034X1) at Amazon.com
HP EliteBook 840G1 Laptop Computer, 1.60 GHz Intel i5 Dual Core Gen 4, 16GB DDR3 RAM, 500GB Hard Disk Drive (HDD) SATA Hard Drive, Windows 10 Home 64Bit, 14" Screen (Used) - Walmart.com