Tandy 600 Programmers Reference Guide BIOS and BIOS Specification
I have this manual. It is merely not scanned yet.
The manual is in paperback form with flat glue spine, and amazingly the spine is still like new, so I don't want to open the book all the way flat to scan on a flat-bed scanner, because that damages the spine.
I plan to scan with a book scanner that only opens the book 90 degrees, such as http://diybookscanner.org/en/intro.html