Reference atomic configuration is one in which one solves the atomic problem (almost invariably the one-particle Kohn-Sham equation within the framework of the density-functional theory) self-consistently. More explicitly, it refers to the set of the atomic quantum numbers (n,l) that one fixes at the outset. In this connection, note that in generating pseudopotentials one invariably solves a spherically-symmetric problem (arrived at through an appropriate superposition of the energetically-degenerate atomic states), so that one solves only the differential equation for the radial part of the atomic Kohn-Sham orbitals, that is R_{n,l}(r). The differential equation at issue is functionally identical to that corresponding to the hydrogen atom and differs from it only by the sum of the Hartree and the exchange-correlation potential (in an exact treatment, the two contributions identically cancel in the case of Hydrogen -- more generally, in the cases where the total number of electrons is equal to 1, but not so within the LDA approximation, where there is a self-interaction error), both of which depend on the charge density, which by construction is spherically symmetric.