Following up on earlier work , Wesolowski and coworkers investigated the case of weakly overlapping pairs of two-electron densities, for which an analytic inversion of the Kohn-Sham equations is possible. Wasserman and coworkers applied numerical inversion techniques to provide accurate reference data for the NAKE in covalently bound diatomic molecules as well as rare gas dimers . In the latter work, this reference data was used for the (re-)parametrization of approximate kinetic energy and NAKE functionals.