I know a German professor with two Ph.D.s who calls himself "Professor Doktor Doktor So-and-so". He doesn't introduce himself like that, mind you, but he uses i

I know a German professor with two Ph.D.s who calls himself "Professor Doktor Doktor So-and-so". He doesn't introduce himself like that, mind you, but he uses it in his .signature file (is it still called that nowadays? the text that's automatically appended to your email).