HP EliteBook 8540P 15.6" Standard USED Laptop - Intel Core i5 540M 1st Gen 2.53 GHz 8GB SODIMM DDR3 SATA 2.5" 500GB HDD DVD-RW Windows 10 Pro 64-Bit - Walmart.com
CMS 16GB (2X8GB) DDR3 10600 1333MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with HP/Compaq® Elitebook 8540P Notebook Sodimm - A13 at Amazon.com
HP EliteBook 8530w RAM Replacement - iFixit Repair Guide
NOKOTION 595765-001 604538-001 KAQ00 LA-4951P Rev 1.0 for HP Elitebook 8540W 8540P Motherboard DDR3 QM57 with graphics slot - AliExpress
NOKOTION 595765-001 604538-001 KAQ00 LA-4951P For HP Elitebook 8540W 8540P Laptop Motherboard DDR3 QM57 with graphics slot - AliExpress
HP 595764-001 - Motherboard for HP Elitebook 8540p 8540w | For use only with CPU 520M 540M or 620M
How to upgrade RAM memory in HP EliteBook 8540w laptop - YouTube