macOS Big Sur 11.2.3 on a late 2009 MacBook : r/mac
MacBook Pro RAM Upgrades (Non-Retina) - OWC
MacBook (13-inch, Late 2009) - Technical Specifications
MacBook Pro: How to remove or install memory - Apple Support
MacBook (2006–2012) - Wikipedia
MacBook Pro - Wikipedia
A-Tech 16GB Kit (2x8GB) DDR3 1066MHz / 1067MHz PC3-8500 SODIMM RAM for Apple MacBook (13 inch, Mid 2010), MacBook Pro (13 inch, Mid 2010), iMac (27 inch, Late 2009), Mac Mini (Mid 2010) at Amazon.com
A-Tech for Apple 8GB DDR3 1067MHz / 1066MHz PC3-8500 SODIMM Mid 2010 MacBook 13-inch
Apple MacBook Pro (13-inch, Mid 2012) - i5 2.5 GHZ 8GB RAM 240GB SSD | eBay
RAM Upgrades For Apple MacBook (2009 - 2010) from OWC
MacBook Pro | Core 2 Duo 2.53 GHz | 13 Inch | Mid 2009 - Techable.com
Upgrade Your Macbook Pro (SSD Upgrade, RAM Upgrade, Optical Drive Bay Adapter) - YouTube
A-Tech 8GB (2 x 4GB) PC3-8500 DDR3 1066/1067 MHz RAM for MacBook, MacBook Pro, iMac, Mac Mini (Late 2008, Early/Mid/Late 2009, Mid 2010) | 204-Pin SODIMM Memory Kit at Amazon.com
Replace your 2009-2012 MacBook Pro HD with an SSD
Apple MacBook Pro with Retina Display (13-inch, 2013) review: Not a Retina MacBook Air, but awfully close - CNET