MacBook Air Pros and Cons (Original, 2008, 2009): EveryMac.com
OS X Yosemite Compatible Macs and System Requirements: EveryMac.com
Where can I locate the Model Number or Family Number on my Mac? Are they unique? What are the limitations identifying a specific Mac using this identifier?: EveryMac.com
Differences Between Late 2008 and Early 2009 MacBook Pro: EveryMac.com
How to Upgrade MacBook Pro Hard Drive (Unibody, 2009-2012): EveryMac.com