How should I reference images found in public domain in my thesis?
I mean, if it would be copyrighted, I would add a comment a la "reproduced with permission from X". If it would be under Creative Commons license, I would add a comment "licensed under XY license".
What about public domain? Should I add some sort of comment to make clear it is public domain? E.g. if I would like to use something from NREL website (http://www.nrel.gov/).