Email, Letter, or Personal Communication
The CSE discourages personal communication as a reference as it is not easily accessible to readers. If a reference to personal communication is necessary, the CSE advises placing the reference in the paper's text and not as a formal end reference.
|... most indicated they admired curvy or heavy women ( 2009 letter from D Singh to me; unreferenced, see "Notes"), supporting the idea that cultural and economic conditions affect perceptions and tastes.
The cited person should be acknowledged in a "Notes" or "Acknowledgement" section that follows the text of the paper. Make sure to get permission from the person to cite him or her in the paper.