X-Com: UFO Defense / UFO: Enemy Unknown on Windows
UFO: Enemy Unknown - Codex Gamicus - Humanity's collective gaming knowledge at your fingertips.
The Best Games Ever: UFO: Enemy Unknown - Manufacturing Base
X-COM: UFO Defense is free on Humble Store, can be used in the OpenXcom open source engine | GamingOnLinux
X-COM: UFO Defense on Steam
Beginner's Guide to "X-Com": UFO Defense Tips and Tricks - LevelSkip
X-Com: UFO Defense on GOG.com
Just beat UFO: Enemy Unknown for the first time on Superhuman. It took 3 real life days of playing for 16 hours per day. Honestly I forgot how good the ending is,
UFO: Enemy Unknown | Old DOS Games packaged for latest OS