Several questions address the PhD. student/candidate issue. However, I stumbled upon the question of the correct abbreviation for a PhD. student. Indeed, one of my co-authors (technically an MSc., she is in the 1st year of her PhD.) asks to be listed as "PhD. student" on my paper. So is there an accepted way of doing that, or should I state "student" in full?
Other ideas would be "PhD. Stud.", "PhD. Stdt.", or something of that sort...