I have a Ph.D thesis obtained from ProQuest. I would like to reuse some of the figures from it in my own work. Every page of the PDF contains this message on the bottom:

Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

How can I find out who is the copyright owner? It is not listed anywhere in the PDF, and I can find nothing useful on ProQuest's website.

The thesis is from the 70s, and the author has not been academically active since then. Tracking him down seems unlikely.