Negation concepts in Sanskrit Grammar

[Kellner]

I am currently working on my PhD-Thesis, a re-edition, translation and
interpretation of two small texts of the Buddhist author Jj at a@nac at ri@mitra,
Anupalabdhirahasyam and Sarvac at abda@bha at vacarca@. 
The background of both texts is Dharmaki at rti's concept of
_non-cognition_ (anupalabdhi). In studying the Dharmaki at rtian passages
related to negative cognition (i.e. cognition of non-existence, however
this non-existence is to be conceived of), it is of course necessary to
have knowledge about Grammarians' discussion on the usage of
negation, especially on the concepts of paryuda at sa and
prasajyapratis at edha. 
My question is: Is anybody currently working on these concepts?
Of course, I am aware of articles such as Cardona 1967 and Staal 1962, 
and a few others, but I am somewhat dissatisfied with all the material
I cam across so far. In other words: Suggestions (further references, 
relevant texts, people currently engaged in research on negation
concepts in Sanskrit grammar) are needed. 

Birgit Kellner
Institute for Indian Philosophy
University of Hiroshima