There is also a "Clascal Reference Manual for the Lisa" (1983) available on the web, and Larry Tesler talked about it (https://youtu.be/OloLXE4I5fw?t=7665). They needed an OO language, but Smalltalk was too slow, so they came up with Clascal.

Some years later Apple joined with Wirth to co-design Object Pascal.

It's difficult to say whether these file are indeed missing, or whether the files referencing them are not used by themselves for the build. I came to the conclusion that I would also have to implement an interpreter for all the build related files (EXEC etc.) and try to reconstruct a complete build with the correct options (which I don't know yet) in order to be able to make any statement about the completeness and integrity of the code. That would take a lot of time at the expense of my other interests. That's why I've put the project on hold for the time being.

Oops, HN adds the semicolon to the URL; I should have used a dot instead.