Imperative and vocatives

Hi everybody,

I'm going to write a short project releted to the interrelation between
imperative and vocatives in written and spoken English.
and the second: the same interrelation but in the spontaneous speech

Does anybody know any interesting paper releted to that subject?
Or maybe somebody has interesting remarks?

Thanks in advance,
Sylvia

[Tdol]

http://www.georgetown.edu/faculty/po...rt_handout.pdf
http://www.georgetown.edu/faculty/po...ects-paper.pdf
http://www.ingentaconnect.com/search...00001/art00010