Books can be attributed to "Unknown" when the author or editor (as applicable) is not known and cannot be discovered. If at all possible, list at least one actual author or editor for a book instead of using "Unknown".
Books whose authorship is purposefully withheld should be attributed instead to Anonymous.
Another photographer who passed away too soon, Ronald Traeger, was an exceptional fashion photographer, who sort of reminds me of William Klein, in that he captures the 'moment.' Another essential European Fashion 60's thing you have to own.
And Twiggy is on the cover! What more can you ask for?