Small separations, d₀₂ (upper panel) and d₀₁₀ (lower panel), shown as function of frequency, for the same three models as in Fig. 3. We note that d₀₁₀ equals either d₀₁ or d₁₀, depending on whether the frequency against which it is plotted corresponds to a mode of l = 0 or l = 1, respectively. Crosses show these frequency combinations when derived from the eigenfrequencies of the original model, while open triangles show the same quantities when the perturbation to the frequencies of l = 0 modes due to the sharp structural variation at the edge of the core is subtracted prior to the calculation of the frequency differences.