Communications that are not housed in a library or archive should be cited in-text only.
... supported by survey results (2007 email from M. Coleman to me; unreferenced).
Number. Author (full name). Letter to: Recipient. Year Month Day. Pages. Note.
4. Allport, Gordon W. Letters to: various recipients. 1930-1967. Located in: Box HUG 4118.10, Gordon W. Allport papers, Harvard University Archives, Cambridge, MA.
When citing a source you haven't read yourself, but which is referred to in a source you have read.
Lilly as cited in Maxwell (3) stated that '...'
Burton (5) quoted Schwartz ...
3. Maxwell F. Phonology. San Franisco: Brooks Cole; 1999.
5. Burton L, Westen D, Kowalski R. Psychology. Milton (Australia): Wiley; 2009.
If no author or editor is present, start your reference with the Title of the item.
5. Macroeconomics, prices and quantities: essays in memory of Arthur M. Okun. Oxford: Blackwell; 1983.
If no location is present substitute an inferred place [Chicago?] or the phrase [place unknown].
If no publisher is present substitute the phrase [publisher unknown].
If no year is present substitute an approximate date [1976?] or the phrase [date unknown].
7. Smythe V. Ant colonies: how they communicate. Canberra: Emu Press; [2007?].
12. Browne JD. Forensic science as a career. London: Tower Publishing; [date unknown].
16. Hawaii [map on the Internet]. [place, publisher, date unknown] [cited 2012 Jul 20]. Available from: http://3.bp.blogspot.com/-6Ckq2CCag0Q/Tr4plGlC-HI/AAAAAAAACLo/CjKZCLjyAvk/s1600/islands-of-hawaii-map.gif