Hi, I'm Jim. I'm semi-retired and currently live near Dallas, TX.
For leisure I record games on YouTube. I'm currently posting Sid Meier's Civilization III videos on Mondays, and Sid Meier's Alpha Centari videos on Thursdays.
The original releases came with a thick paper manual, a keyboard template, and a printed tech tree. On some CDs the manual is provided as a PDF, and sometimes a PDF manual is in the application folder.
Gog.com includes the manual PDF as a downloadable item after purchasing the game. Steam has the PDF manual available online.
Note that the in-game Civilopedia help system is very thorough, and in some cases more accurate than the manual. Especially when playing custom rules, scenarios, or conquests.
The only place I know of to obtain Alpha Centari is on gog.com. The CDs use copy protection that no longer works on Windows since 2015.
The original game came with a paper manual and printed tech tree. The manual was also in PDF form on the CD.
Gog.com provides the manual as a download after purchasing the game.