What is the best public, unambiguous, non-YouTube reference I can cite for the late David Mills' initial FTP work?

I see that the wording on his Wikipedia page has the ambiguous phrase "had the first implementation of FTP", which has been flagged as needing clarification, so I intend to provide it.

In both this interview:

... and this video recording of Mills himself giving a lecture at UDel:

... it's quite clear that it's literally true - he authored, compiled, installed, implemented, and tested the very first (and apparently second) FTP server. But Wikipedia's guidelines discourage YouTube-only citations, and the text in the interview seems insufficiently detailed to have citation value.

What is the best reference I can cite?

Thanks!