I have a question about the correct way to write a reference to a private communication. The other day I was making some corrections in the proof of an article that will soon be published. One of the questions/comments from the editors office was that regarding a referenfce to a private communication (an e-mail). The reference was written Ref. XY F. Surname ,private communication. which is usually fine (I try to avoid references to private communications, but sometimes it can't be helped). Hower, this editor wanted me to add the date (of the e-mail). I this a convention? I've never come across it before. The paper will be published in an AIP physics journal, if that makes a difference. btw, sorry if this is the wrong subforum. I wasn't sure where to put it.