the boundaries of language

Does anyone know of any literature on the closure problem for testimony: that if one gains knowledge that p from someone's assertion that p, and one's knowledge is closed under known implication, then one knows (or is in a position to know) that the asserter was telling the truth? There seems to be a little bit of discussion in the SEP article on Epistemological Problems of Testimony by Jonathan Adler, but I don't know of any other discussions in the literature.

(There are, of course, a number of general discussions of closure, and of other specific closure puzzles such as other sceptical arguments and the lottery paradox. But I'm hoping specifically for references on the problem for testimony).

Labels: Epistemology