Personal Communication
Some references can be grouped under the heading of “personal communication.” These include private letters, memos, emails, online discussions, personal interviews, telephone conversations etc. that have occurred between yourself and another person. As these personal communications are private and often temporary they cannot be accessed by anyone else. Therefore they are not included in the reference list and are only cited in the text of your assignment.
NB: Include the initials as well as the surname of the communicator
According to D. Tennant (personal communication, April 18, 2012)…
OR
…as it has been identified (D. Tennant, personal communication, April 18, 2012).