The files here come from a snapshot copy of Fourth Edition Unix sent to the
University of Utah on tape in June 1974. The tape was found in 2025 and sent
to the Computer History Museum to recover the contents. Subsequently, the
tape's contents were uploaded here:

https://archive.org/details/utah_unix_v4_raw

by Thalia Archibald. From here, Angelo Papenhoff used the contents and
wrote up the details of how to install the tape to an RK05 disk and
boot it using either a simulator or the real hardware.

The files, ultimately, have been retrieved from Angelo's site:

http://squoze.net/UNIX/v4/

Angelo's README file has been renamed as aap_README, which you should read!