I've never understood why somebody would want to read a book sent to them unsolicited by person unknown when there are so many other books out there and not enough time etc etc.. (edcyzewski.com)
Ask them to think about the rings of responsibility — the ways in which they are responsible to themselves, their friends and families, and a wider circle of people unknown to them. (gse.harvard.edu)
Even people unknown to officers can be identified and, with a few quick searches, revealed as a person with recognizable characteristics or about whom certain predictions can be made. (prawfsblawg.blogs.com)