Also known as Spruce Technologies, the specification is available [here](https://web.archive.org/web/20091028173024/http://geocities.com/McPoodle43/DVDMaestro/stl_format.html). Sample files: [DVD Studio Pro.zip](https://github.com/sandflow/ttconv/files/9742866/DVD.Studio.Pro.zip)
Also known as Spruce Technologies, the specification is available here.
Sample files: DVD Studio Pro.zip