Areal prefix

[James Crippen]

I'm looking for references on the form and function of the areal
prefix in various Athabaskan languages, as well as historical
reconstructions in Proto-Athabaskan(-Eyak) and Proto-Na-Dene (PAET).
It's difficult to search for "areal prefix" since I get a lot of false
hits. Anyone have good references at hand? Published or not, I don't
mind.

My reason for asking is that I'm investigating a probably related form
in Tlingit, where it appears to overlap with the indefinite human
object prefix.

Thanks,
James