impurity potential has a much shorter range of order $\sim
1\AA$ [@LLWang:2005] compared to this ansatz, it is possible that the phenomenological parameters used in these models represent dynamically generated quantities in a more complete theory. Finally, the observed Zn conductance pattern has also been obtained in theories which describe the Zn as a Kondo impurity[@vojta] and pairing impurity,[@andersen05] respectively. We now discuss each of these scenarios in the context of the resonance extinction problem.

Zn as Kondo impurity
--------------------

Motivated by NMR measurements[@alloulnmr; @mahajan; @bobroff; @mendels; @julien] showing that nonmagnetic Zn impurities induce a local spin $1/2$ in their vicinity, it was proposed that the LDOS data could be understood within a nonlocal Kondo model.[@vojta; @vojtabulla] With a proper choice of a large magnetic potential coupling the nonlocal spin associated with the impurity to the conduction electron bath, the observed spatial pattern could be reproduced. This requires, however, the assumption of a very weak potential scattering at the Zn site. An interpretation of this work accounted also for the disappearance of impurity resonances in large-gap patches[@vojta; @hoffmanthesis] by assuming that such regions were underdoped and therefore poorly screened. In such a case, the Kondo temperature $T_K$ would fall below 